My point of view is that if it was just a decision for someone that'd be alright and should be supported nonetheless. That being said I've never met someone who is trans and claims it was a choice.

If it's 'just' a construct then it is a fundamental one that occurs at a very young age and you can't just simply change that, so it's not really a choice. Like the trunk of a tree.

Also there are many reasons not to transition medically. There are many risks involved and requires considerable resources. For example getting facial hair removed can take 30 sessions, so even if it's free it costs you a lot of time.

Imagine you woke up in the wrong body tomorrow. Sure, you want to go back to the right body, but you might be OK with it as long as the people around you just see you for who you are. This can be done with a social transition, some clothing and makeup.