Lets break down what you said claim by claim.
1. "That 10-15% of teens aren't trans": 97% of teens aren't trans. There have been numerous studies showing that approximately 3% of teens in the USA are trans.
2. "It was a post COVID phenomenon": Trans people have been around long before COVID. There is a little bit of basis to this claim though, and it is likely attributed to the fact that due to lack of social interactions, less trans people were bullied or harassed in person and so felt safe enough to be known as a trans person.
3. "TikTok... was a large reason for that": This has no factual proof as far as I know. If many trans people use TikToc, that does not necessarily mean TikToc makes people think they are trans. However, if there is any correlation, it may be because there is a community of like-minded people on TikTok that do not deny trans peoples identities. Having that support may cause someone to be more open about their transgender identity that without that support.
4. "Depression... was a large reason for that": Depression does not cause people to be trans. But the stigma, critique, and harassment that comes with being trans can and does cause depression.
5. "A sense of belonging was a large reason for that": This much is mostly true. If someone finds a group of people with similar beliefs, of course they will be more open about it. Would someone admit to being trans at a Trump rally? Almost certainly not. But if that person were to attend a Harris rally? It is much more likely. That doesn't mean it is a fad or a trend that just comes and goes, it means that they feel safer and comfortable with people knowing that. Another example (this is a bit extreme, but still helps my point). In Germany in Hitlers era, would someone admit to being Jewish? No. Because it would not be safe. But does that mean they are not Jewish? No. They are still Jewish.
6. "Not nearly as many kids today identify as trans as last year, the year before that or the year before that.": Can you cite a study that provides evidence for this? I have not seen similar trends over the past few years. But this past few months, I have. It relates to point 5. With the incoming Trump administration, harassment and bullying towards trans people has already started getting worse, even in one of the most liberal states (I'm in California). Trans people do not want to be targeted. And so there are SOME trans people who stop being open about being trans, but most of them are still trans.
7. "Guidance counselors recognized all of those things and though were supportive, clearly didn't believe it to be a lasting fad.": In many states, the laws force counselors (and all school admin) to be supportive and recognize students identities. However, especially for counselors, this is unnecessary. Counselors typically have degrees in psychology. They would understand LGBTQ matters much more than the average person (who isn't LGBTQ). It is not woke ideology, but rather science backed by many studies (not to mention every major medical association has taken anti-discrimination measures to protect and support trans people; and therefore we can assume that they recognize that being trans is not a fad).
8. "For you not to recognize the impact of social media on incredibly impressionable brains is literally insane.": Of course, social media does massively affect a teens brain. However, one thing I believe you are not taking into account is that as of recently, more and more social media platforms have been gaining a more conservative user base and/or has been stripping protection policies from LGBTQ people, allowing more discrimination and harassment. This can also help contribute to points 5/6. Teens are being bullied and harassed more online for being trans, leading them to be less open about being trans. But users of more liberal platforms would likely be more open about being trans. (note: this is coming from a trans teen who is adamantly opposed to mainstream social media. I have never downloaded or used insta/tiktoc/facebook/twitter/x/etc and have even taken measures to try to get my school to ban cell phone use on campus.)
9. "And don't try and tell me I'm some right-wing trans denier. Cause that's not the case at all.": You may not be a right-wing trans denier, but you do come across as a trans denier nonetheless. You claim that 0.0001% of the population is actually trans where it isn't a fad. In reality, among teens in the USA it is actually around 3%. This has been shown along with similar statistics by many studies.