You can't discount pushback against pushback for some of the sociology here.

If the uniform response to the surfing, tik-toking, college student who actually is 60 years old but passes as 22 visually was as negative as responses to trans people often are, you might very well find more strident anti-ageism measures.

The problem with using counterfactuals as sociological thought experiments is that it's very hard to think them all the way through due to all the feedback loops in how people react.

As a practical matter, there isn't a substantial cohort of people with a very deep identification as a wildly different age, and there's a huge cohort of people with an internal identification as a somewhat different age. Furthermore, we don't stratify roles extremely sharply by age. So the parallels all fall apart when you push on them a little bit, so our ability to reason by analogy to transage identification ends up poor.

Transracial identification is a better parallel, because there are people who strongly identify as a different race than they're "supposed to". So I fully agree that the pejoratively hostile stance of the supposedly tolerant open-minded crowd towards transracial identification is extraordinarily hypocritical.

But as I said, this tells us nothing about what the proper stance is, only that the two stances are not easy to reconcile.

If your argument is, "Pick one!" then sure. If your argument is, "trans identity is wrong!" then no, the parallel doesn't establish that at all.