i wanna say sit on it YESSSS

ITSNOT SWITCH I don't understand how hard is it for it to understand just because someone is cute or shorter than their partner doesn't make them automatically the bottom its their dynamic and I usually advocate for switch but this always happens for a specific type of couple

In the special doujin it's stated that they've tried switching but they prefer the way we see them in the manga. I believe the comment was referring to that.
In irl gay couples some have a very solid 'role' and some don't really care. I think in this case both characters didn't care what role they had but while trying a different way discovered their preference, which is very cool!
I understand you thought. I myself I don't like when the small character instantly becomes the 'girl' without considering their own opinion. Bigger, muscular bottoms are refreshing in that way but become a new archetype. What I really like about this story is that they found their role through (we assume) talking and trying instead of just 'who looks more bottom-ish'.

Sorry for the long reply, have a good day!