ok im going to unpack this, bear with me cause there's a lot here, so here we go
Masking applies to the magicians own aura.
Masking also applies to the magicians own astral form (while using astral perception or astral projection the magician can change his or her astral form so it look like another astral form; for example the astral form of a spirit or an active focus).
agreed, you can also use it to make you look like a mudane or whatever else (a fly, a spirit etc).
Masking also applies to the aura of up to initiate grade number of bounded foci
agreed
(no requirement on the force or that they have to be in the magician’s possession).
this is unlikely the intent or useful as a ruling.
Masking is specifically about editing your aura and the magical things you carry (foci).
Imho it would be far more logical if the foci leaves your presence it's no longer part of your aura and so therefore not subject to being masked. This is also true if you fall unconscious or go to sleep, your masking is no longer active. If this were not true then you could maintain masking on your foci wherever they are in the world, no matter how long ago you touched them. which is clearly nutso.
My take on this is that you may use Masking to hide the magical aura of your non-active bounded foci from other magicians (by making them look mundane) but you cannot hide or change their astral form once you activate them.
I disagree with this as it's clearly against RAW where it specifically says you can make your aura look like anything you want (and by extension your bound foci).
Extended Masking applies to the aura of active (explicitly anchored, sustained and quickened) spells (no requirement on number of spells, the force of the spells nor that the target of the spells have to be the magician).
Extended Masking also applies to the aura of up to initiate grade number of imbued or attuned items and alchemical preparations that are in the magician’s possession (in addition to bounded foci). Force of the items must be less than the magician's Magic
agreed
Personally I don't think Extended Masking make sense since both active spells and alchemical preparations have astral forms. Changing the aura so it look mundane would be pointless since the astral form would be obvious for anyone that can sense the astral.
the above supposition is only correct if you deny that foci and auras cannot be disguised to look mundane. which is not the case afaik. therefore I disagree.
Even if it was changed so that you can use Extended Masking to also change the astral form to another astral form (so an active spell look like an active focus or an alchemical preparations look like a spirit) will not really help you look mundane either.
again this relies on your interpretation that masking cannot make a magically active person look mundane. lore and raw say otherwise afaik.
My guess is that it is not the same author that wrote Masking that wrote Extended Masking....
probably correct.
back to the issue at hand, I still hold that because Masking (and Extended Masking) is meant to allow you to change your aura (and any magical effects or items attached thereof) and moreover that it ceases when you fall unconscious or go to sleep that therefore using Masking on quickened spells you place on others is not viable. Their aura is not yours. Masking is personal not a service you can offer to other people.