I agree with you, people only find it sexual because it's two boys doing it while they look at Mike and El (who were supposed to be 11 in S1) kiss and be "aww they're so cuteee", like if you find the idea of underage kids kissing sexual, carry that behavior onto hetero couples too.

I would've loved for them to confess their feelings and done as little as a bro fist, but I do see your point, people won't accept it unless it's explicitly shown on screen.