Everyone who studies that sort of thing has told me that viewing ancient roman sexuality through a homosexual vs heterosexual lens is not quite right. You need to look at it more through who's the "passive" vs "active" participant.

That it was socially acceptable to be a man and penetrate someone else regardless of their sex, while it was frowned upon to be a grown man and be penetrated.

Similarly, to receive oral from someone else was fine, but it was frowned upon for a man to perform oral on a woman.