May Allah guide you (this is sincere not out of hate don't take it the wrong way) but how can you even say this? Biological sex is an objective truth and medically verifiable and observable. Very similar is not the same. There are people with mental ages below their actual age. Are they also younger than the age they go by? Should they also have hormone therapies? Should they have age reassignment surgery 'if need be'? This is nonsense.Muslim? Maybe
And no, they are not lying to themselves about their true gender. Studies have shown that transgender individual's brains are very similar to their desired gender.
If you can suggest a solution to this dilemma then I'm pretty sure all transgender people would take this treatment. But so far the only way to help them is to put them on hormone therapy and do gender reassignment surgery if need be.