If we had evidence that a person who transitioned, or a person who transitioned medically, was more likely to take their life than that same person denied the chance to transition, then that would be evidence we should consider seriously.
But we don’t have that evidence. We can’t compare the people who transition now to people like them ten or fifteen or twenty years ago who weren’t able to transition, because we can’t identify the people twenty years ago who would have transitioned if they’d been able to. We can’t identify “people like them twenty years ago.”
tl;dr We can’t tell the difference between “Transitioning makes people more likely to kill themselves” and “People who are more likely to kill themselves are also more likely to want to transition.”