Puberty is very much part of the medical hormonal transition experience according to most verifiable accounts.
Unfortunately people often behave like complete asses when in puberty, so trans people in that stage of transition often behave like total ass hats too. It wears off once the puberty of the new gender is done. Unless they were total assholes before transition too, in which case they are stuck with it.
It's interesting to me to see posters stating they would be fine with a trans man in a female space, especially if they were told the person was born female.
That's not been my experience of it at all, though if I'd taken a guess before actually being in that position lots of times I would have thought I'd be just fine with it.
It turns out the psychological response is way more complex than that, and that once a person starts reading as male (I mean the small perceptions that our brains use to establish gender) I'm really not comfortable with them being somewhere I would ordinarily only share with females. And this includes super close people whom I've known for years and years as their original gender. You'd think the brain would be able to override what it sees and hears with what it knows, but that's not the case here.
And I think there's a further problem with the argument I often see here that trans men would be welcomed in women's spaces and that therefore it's not anti trans to exclude trans women from them.
Are you going to take their word for it? Or ask to check their pants? Because trans men are often really really hard to tell apart from youngish natal blokes. And I get that you might think at this point that you'd be fine with it, but bear in mind that your brain will be busy telling you there's a bloke there, because the person in front of you will likely look and sound very much like a young bloke, and will be dressed as and behaving as a male.
So given that males are hellbent on getting into women's spaces (I'm paraphrasing the GC prevailing wind here) surely if trans men were welcomed into women's spaces then it would be a shitload easier to just say you're a trans man to get access, than to present as a trans woman.