Some people claim that some cis women experience the same sort of autogynephilic things that trans women do. This claim has some serious problems, but so does its negation. However, let’s suppose cis women do experience such things. Does that mean the typology is bunk?
No. To some degree, autogynephilia in cis women threatens certain aspects of the model, such as erotic target identity inversion as the explanation of AGP, since this means we would not expect it to be possible to straight women to experience autogynephilia. (That said, women seem more bisexual in some sense, so it’s not a disproof of ETII…) However, ETII is only one aspect of the typology, and many useful things can still be derived without it.
However, what about everything else? Does it suddenly prove that AGPs and HSTSs are somehow the same? Or that AGPs are feminine? Not really. We could imagine any number of reasons for why cis women might experience autogynephilia. For example, consider Michael Bailey’s model of female sexuality. He argues that women don’t truly have a sexual orientation, so that they can be attracted to women if coincidences permit it, and he argues that this lack of orientation extends to the auto/allo dimension of sexuality. I doubt he would buy the argument that cis women are autogynephilic, but if cis women are potentially-gynephilic and potentially-auto(andro)philic, then it seems like there’s nothing that would prevent potential autogynephilia.
We could imagine lots of other models. Perhaps the causes of AGP in natal males and natal females isn’t even the same. However, there is one model that seems dubious, and it is the model which asserts that femininity is the cause of AGP in both natal males and natal females. Why is this problematic? Well, HSTSs and gay men don’t seem especially autogynephilic, despite being unusually feminine.
So, why do some people care so much about arguing that cis women experience autogynephilia too? I think they feel that the autogynephilia argument goes “Some MtFs experience AGP, therefore they aren’t women!”, and I’m sure some people use an argument like that, so it’s not an entirely unjustified reaction. However, the goal for me isn’t to decide whether trans women are women or not (my takes on that can be summed up as “transition is legitimacy”); instead, I’m trying to understand and predict people’s gender feelings, and by far the best model for this is autogynephilia.
The alternative model that some propose is that “trans women are women, and this explains both the autogynephilia and the desire to transition”. That’s not a real answer, though! What aspects of womanhood causes this? How do we know? Autogynephilia is a much more effective and justified explanation here.