Your discussion is excellent--it really gets to the essential problems with Stock's views and arguments.

However, I wonder if the above sentiment has been cast aside with too little thought.

I agree that it at least certainly appears that a lot of non-trans people have a plenty strong sense of gender identity. (Some explicitly confirm it.) One way to take the quoted statement is "because my gender identity and sexual morphology match, I have a poorly-developed sense of the distinction between such things, so I'm making confused claims."

But there are also people who report being agender or genderfluid. If one trends that way, but is content to accept one's own body as it is and the concomitant societal roles, what would one say? Mightn't one correctly report on one's feelings by saying, "I have no gender identity, I just am a woman (=morphologically female, and able to play the expected societal role)"?

So I'm not entirely sure this can be so quickly dismissed. People can have legitimate reasons to defend aspects of their status despite not having any deeper connection to it than it being who-they-are. For instance, someone who weighs 100 pounds (45 kg) might not have a size-identity as a "small person", but they might very much object to being placed in a judo competition with a 220 pound (100 kg) individual who "feels like a small person" (even if that feeling is extremely deeply rooted psychologically to the point where it causes them distress when they or others view themselves as not-small). So one can't take the mere appearance of concern as conclusive evidence that, in fact, the gender identity is there.

Thus, reports like the above might not all be confused, though to me it seems likely that many are. Those who originate the idea and assert it most stridently may, in fact, simply be accurately reporting on their personal psychological state.

In particular, if one does have this psychological state, it would be especially hard to understand trans-as-identity as opposed to trans-as-ideology, because while they could envision accepting an ideology like that (we're postulating that they kind of already did accept the normal-ideology of you're-who-you-are without a strong intrinsic feeling of i-am-this), but they don't have experience with that sense of identity so it doesn't compute. In contrast, people with significant gender incongruence are in a good position to understand gender identity without incogruence, but probably have particular trouble relating to the idea that gender might be governed by ideological beliefs (after all, it already didn't for them, where the ideology is society-standard).

If true--and I don't have much evidence, just a supposition--then it's probably very important to recognize it if one wants to be able to have a meaningful dialog with people who think differently. Without explicit recognition, I think the different perspectives would be so great as to make communication difficult at best.

[Aside: the weakest part of your response is the medical side of things. You note that Stock isn't a medical professional, but neither are you--though admittedly cognitive science is more medicine-adjacent than is philosophy. So either your criticism of background is unfair, or the stance is somewhat hypocritical. Furthermore, if you take Stock's removal of distress quote seriously, most of your medical care parallels don't work, because most of them are predicated on the danger of distress. However, why remove distress or risk thereof?! We don't want people to be in distress. Some of your statements verge on being out-of-touch: being concerned about fertility is hardly creepy given the vast amounts of money spent on fertility clinics and the documented change in the strength of feelings about having children between, say, 15 and 30, for many people. You do have very good points also: "this goes completely against expert medical consensus" is extremely relevant (and largely true, though it depends which claim we're talking about). But, anyway, overall it's a very good discussion and case against a Stock-like point of view.]