You're going to 100% get some heat for this one (due to the near-Pavlovian hostile response some people have to the "T" word being used to describe something), but I agree.
Mahiro really revels in the various aspects of being a girl, but still very much wants to be seen as a reliable "oniichan" figure. It's why I say "any pronouns work for Mahiro". In a sense Mahiro comes off as a very cute young girl (helped in no small part to Marika Kouno's incredible voice acting) but with an almost boyish fire to her.
Minato though... man, even a DROP of experiencing the feminine and that kid's heart is singing. Think about it; if you turned Mahiro back almost right away from the first or second chapter, they'd be like "whew that was weird but I got past it somehow". Minato in that position would probably be agonizing over pervasive thoughts about asking to become a girl again, instead of having to let it go forever. That is peak gender feels.
(Mahiro does ultimately develop gender feels too, but they didn't take root this rapidly)
Yeah, I've long thought Mahiro's gender is mostly irrelevant - most boys/men in Japanese stories seem to be very invested in being
manly men, and Mahiro definitely has some of that, but it's more about being invested in certain things that are generally seen as manly but aren't inherently gendered (even in Japanese culture), like being a responsible older sibling, being responsible for the safety of the household, and (most importantly for the story and character growth) being strong and reliable. For Mahiro, that last one ended up being read as "independent to a fault" (a fairly common "manly" way of thinking, sadly).
Most of what drove Mahiro's descent into neet-dom was that desire to live up to the common misreading of being strong and reliable, and
failing to achieve that (particularly contrasted with Mihari); the core of the whole story and Mahiro's character arc is learning that you can be strong and reliable and responsible without needing to be independent to a fault. Being genderbent is just the backdrop, not the point - the real point of the whole thing is Mahiro realising that it's okay to need help because sometimes you absolutely
need help; recognising that the people you care about won't suddenly despise you for needing (and accepting) that help; and realising that it's possible to both accept help and support from people and to
give help and support, often at the same time.
. . . the fact that young girl == small bladder == surprisingly common fetish . . . . . I guess we're all still here after 90-odd chapters, so we can overlook that?
Minato, though, really does seem like a nice kid with no particular hangups who just hadn't thought about any of this until now . . . I do hope we see more of this, because it's definitely a more realistic approach to someone reassessing their understanding of their own gender identiy and preferences, and it's nice to see.
. . . . also,
wow it's hard to write something like this without using pronouns at all . . .