Not sure about that, I think the seme only started to question his feelings,truly; when he accidently caught a glimpse of the uke with the senpai and even then he admitted he wasn't sure then if it was friendship or love... Plus the seme never told until much later about catching those two together. I think this started to make the seme question his feelings but only maturity actually cleared up what he felt in his heart
I mean the seme’s confused that time so there’s a big chance that he might reject him and things can get awkward for the uke if that happens.
Good point
I can't help but think if the uke confess his feelings to the seme way back in high school, i think his feelings will be reciprocate then they will become a couple and the kid will not be born.,i just think okay.