Apologies for the lack of clarity. I'm not writing rules, I'm making a forum post, but it is important that you understand what I'm saying. I'll be more formal.
Re-clarifying
Shadowrun (SR) books suffer from a lack of clarity in rules, fluff, and guidelines. This makes it difficult to determine the line between rules, fluff, and guidelines. I define game rules as "instructions governing how to play", rulings as "ways of interpreting these rules," fluff as "text that enhances the plot or tone of the book," and guidelines as "advice that aids the GM in creating rulings."
I define the rulings in the Shadowrun Missions (SRM) FAQ as "SRM rules" because they are rules within the context of a SRM game: they are not meant to be adjusted within official SRM games.
There are cases where SR materials can be clear. The SRM rules show concise and direct language. I use them as an example on how to create a rule that is understandable and has clear meaning.
There are cases where SR materials are not clear, but this serves its purpose. For example, the guideline cited previously on p. 36. Being unclear is fine in a guideline since it is intended to aid interpretation, rather than be clear direction.
There are cases where SR materials are not clear, to the extent that this no longer serves its purpose. This is the case with time tables. Time tables are also a case of SR assuming that the GM has game-mastered or at least played RPGs before, which is a sin committed by many RPGs. It's also bad design.
There are cases where SR materials appear to be clear, but do not match the RAI at all. For example, the rule for GelWeave states:
For GelWeave, the armor can resist up to the rating of the GelWeave in incoming damage against each attack. However, the gel becomes rigid when absorbing more than a small hit (1 DV) each round, and reduces Agility, Reaction, and meters of movement by (DV resisted – 1) for three combat turns. These reductions are cumulative across combat rounds, and the duration for all reductions is three rounds after the latest hit. If Reaction or Agility is reduced to 0, the wearer gains
the Immobilized status
This rule seemed clear to me. The GelWeave rating is the amount of damage (DV) resisted. The penalty is DV resisted - 1. Therefore, if GelWeave only resists 1 damage, the penalty will be 0. GelWeave rating 1 will only resist 1 damage, and therefore, will never incur penalties. I later learned that this does NOT match author intent.
And then, there is anticipation.
Getting the Train back on Target
Anticipation (Multiple Attacks, Ranged Attack): You played this combat like a game of chess, using each strike to direct your opponents to a particular spot. Now they’re there, and you can attack without even looking at them, since you’re firing at a spot, not a person. When performing this Multiple Attack, roll your full dice pool for each target. Cost: 4 Edge
This seemed like one of the times where SR writing blended fluff and rules well. The first two sentences are fluff, and they also provide guidelines for retconning why this works within the game world fiction. The subject and last sentence are as clear as they can be. When making a multiple attack that is also a ranged attack, you roll your full dice pool against each target. So, if you have 20 dice and split your attack between two targets, each target faces 29 dice, for a total of 40 dice rolled. If you split it among four targets, each target faces 20 dice, for a total of 80 dice rolled.
Caveats: If you are using a main weapon and an off-hand weapon as part of this, only your main weapon gets the benefit per p. 100: it would be 30 dice total or 50 dice total (20+10, or 20+20+5+5). A GM could make a ruling that cannot even use anticipation if your off-hand is part of the attack, so it only applies if you make multiple attacks with your main hand weapon. If you have Ambidextrous, you do not take this penalty.
You say Firing Modes play into this, but they seem equally clear:
BF: You’ve got a fancy gun that pumps out multiple rounds with a single trigger pull. You can fire four rounds in an attack. You can shoot a narrow burst, which decreases the Attack Rating by 4 and increases damage by 2, or make a wide burst and split your dice pool between two targets and count each as a SA-mode shot.
So with a wide burst, you split dice between two targets, and treat each as a SA-mode shot. This is where we enter confusion: should this count as a multiple attack? If you take this section alone, the answer should be "no" because Multiple Attack is the name of a specific Minor Action, and nothing in this states you must do this. However, if you read the entire section, you see FA:
This mode allows multiple attacks without using the Multiple Attack Minor Action.
You could interpret this to be the 'exception that proves the rule:' Because FA specifically allows multiple attacks without using the Multiple Attack Minor Action, the others do not allow it. (IE, "No parking on Sunday" means that you can park every other day of the week. This is the interpretation of 'exception that proves the rule' that courts of law in the US use.) You might be able to interpret this to mean when you make a wide burst with BF, you are using the Multiple Attack minor action, and therefore, must use that minor action in conjunction with the wide burst.
Personally, I'd make a ruling that that is too much of a stretch: you should evaluate BF on its own.
However, I don't think you need either mode to exploit anticipation. This is the rule for "Multiple Attack:"
A character can attack more than one opponent, assuming ammunition, reach, and enemy placement allow it. Split your dice pool evenly among all targets, or if you are using two different forms of attack, use half the dice pool for each, rounded down. This action must be used in conjunction with an Attack Major Action.
The restrictions here are based on ammo, reach, and enemy placement. There is NO restriction on how fast it takes for you to aim and fire your weapon, or on which firing mode you use. You could use a strict SS or SA weapon with this. Take the FN P93 Praetor, for example. It has a SA mode and a clip of 50, allowing you to make 25 SA attacks before you need to reload. This would normally not be a good idea, since you round down for multiple attacks; no 6E character will have a dice pool of 25. However, let's say you use Anticipation, you have a dice pool of 5, and you have Ambidextrous.
You use a major action and a minor action to do multiple attacks. Since you have ambidextrous, you can use edge actions with an off-hand weapon as well. You wield two FN P93 Praetors, and have enough ammo to make 25 attacks with each one. That's 50 attacks, with 5 dice each, for a total of 250 dice and base 250 DV (With the +1 from SA). Your face who used Agility as a dump stat isn't looking too shabby now, are they? (Granted, the attacks might not all hit, and the first time you glitch, your now-irritated GM will probably make your gun explode, halting the attack).
I reject the excuse of "English Language" because there are instances even within SR materials where authors use language in a way that is clear, or in a way where the vagueness best serves their purpose. I don't even think firing mode plays into this as much: we can use a normal SA/SS attack with the normal rules for multiple attack and achieve ridiculous results.