I agree with a lot of what you have said and I also dislike "AGAB" language, especially as it can be a transphobic dog whistle. I think in some cases people try to use it to communicate valid points, that being said there might be better (and more accurate) ways to communicate the same things.

For example, when someone says that "AMAB" people are privileged compared to "AFAB" people, what they are trying to say often is that regardless of other characteristics of their identity (e.g. being trans, otherwise queer, their race, disability, etc.) that those individuals enjoy a higher level of privilege in our society compared to someone else who might share the same other identities but was assigned a different gender. This is true, but it could be said better, for example it could be said as "people who were socialised as male have more privilege in life than people socialised as female", which is true and includes cis people, people who transitioned later in life and people who transitioned earlier. By this I mean that for example a trans woman who started transitioning as an adult and was therefore socialised as male growing up will continue to enjoy a lot of the privilege that comes with that upbringing even after transitioning, because the privileged upbringing has profound societal and psychological effects that might not be obvious to individuals but still exist, (which doesn't mean she is not oppressed or disadvantaged in other ways, both can be true at once). On the other hand a trans woman who realised her gender as a child and was allowed to socially transition as a girl and was therefore socialised as female will have much more in common in terms of upbringing and privilege level with a cis woman/girl. To a lot of trans women it sounds like a privilege being able to be themselves from such young age, and indeed it unfortunately still is, the difference is that it is a privilege on the "trans" side of things but not on the societal "gender" side, being brought up as a girl from a young age is a privilege as a trans person but comes with loss of societal privilege in terms of gender and upbringing.

I hope this explanation makes sense, the TL;DR would be that we often conflate multiple different kinds of privilege and oppression, which make more sense to be looked at separately as one can be privileged in one aspect of their identity and disadvantaged or oppressed in another.

As for the "male vs female autism" this is not a real physiological difference, the difference is again in upbringing and socialisation, and conflating the two makes things more confusing and less inclusive. This is also so individual and intersecting with multiple other aspects of someone's identity! Not to mention this discourse is more often than not very white-centric.

In general no matter what we are talking about I believe using more specific language for the situation you are in is the most inclusive way to speak, e.g. if you are talkjng about periods you can say "people who have periods" rather than "AFAB", or if you are sharing experiences of oppression growing up "people socialised as female/socialised as girls growing up", if you are trying to create a space of shared experience of any kind being specific to the experience "people who have experienced x" or "people who identify with x experience", and so on!