I read the essay by Sullivan, and I don't see anything in it that ought to even be considered controversial.
It's extremely interesting to me that he counts mainstream medicine as one party on his list of "the woke establishment". And it's not the first time I've come across this: it's been directly and indirectly claimed within this very thread. To me, either he doesn't understand what the word "woke" means (and he's clearly using in in pejorative sense here - which in itself is also interesting), or he is accusing the world's expert clinicians, psychiatrists, & psychologists of being either bamboozled, misled or mis-judgemental in the way they now understand transgender identity. Which (again, IMO) is a pretty breath-taking dismissal of the actual scientific experts in this field: the individuals and associations who have carefully studied this issue for decades now, and who have interacted with thousands and thousands of transgender people.
I think the issue is that there is a limit of medical expertise so that even the experts are not all that expert.
I haven't contributed to some of the recent scientific discussions because I don't have any real information to contribute, but I think that the large number of detransitioners suggest that there's a lot to learn, and that mainstream medicine, as it exists today, might not have much expertise to offer. Science should be judged by results, and when one of the results is that patients come to regret an irreversible treatment, that doesn't speak well for the science that led that treatment to be prescribed.
Moreover, sometimes the "leading experts" are really just the most prominent voices, and sometimes the people who have the biggest stake in a particular outcome. I'm sure that the Tavistock clinic was just overflowing with the best experts available.
In psychological realms, this is even more likely to be the case. Sigmund Freud was a leading expert. Indeed, that doesn't begin to even describe his level of reputation. However, expert or no expert, a lot of things he said, and which formed the basis for a lot of treatment, were just plain wrong.
Finally, medical expertise isn't the same as social policy. A medical expert might be able to describe the experience of living a transgender existence, but they can't answer the question of whether they ought to compete in the female sports division. That question is not one where there expertise is applicable.