Ok, yes first of all it's unnecessarily confusing that there's two different kinds of mechanics that share the "Called Shot" name. But for now, it helps to clarify that there ARE two completely different mechanics that are both called Called Shot.
First kind of Called Shot is spelled out in the CRB on pg. 41 where it's technically named "Call a Shot", but is narratively referred to as "called shots" even in its own descriptive fluff. "Call a shot" requires the expenditure of a Minor Action in conjuction with a Major Action to execute an attack. Additionally, it incurs a -4 dice pool penalty, but for the price of those two costs you gain +2DV to your attack.
The next kind of Called Shot is a categorical grouping of Edge Actions that all bear "Called Shot" in the name. Note that again these have nothing to do with the "Call a Shot" minor action from page 42. Here, these Edge Actions incur no cost in action economy nor in dice pool... instead you pay in Edge. And they give different benefits than "Call a Shot".
It's unnecessarily confusing due to the similarity in terminology, but hopefully that clears it up. At least until we open the cover on Firing Squad, right?
The sidebar on p. 103 of Firing Squad is indeed referring to pgs. 47-48 of the SR6W book. What it's saying is that if you use a Called Shot that is an Edge Action, you don't have to also pay the Minor Action for "Call a Shot" nor take the -4 dice penalty.
I'd also add that this gives reasonable inference that you can't do BOTH... that is pay a minor, take -4 dice, spend X edge, and then gain +2DV AND the edge action benefit. Do one or the other.