So how could that define manhood?
Societal expectations. If enough people think it does then it does. Doesn’t mean non-men can’t do it, but they might get ostracized for it, just like men are when they do certain female-coded things. Why is blue for boys and pink for girls? Why are high-heels for women only? Doesn’t have to make any actual sense, it just kinda is right now, even though it wasn’t always the case.
It very much is something you’ll find in advice columns for women.