Let suppose "gay" is defined for male porn consumers as the amount of penises in a video. Straight porn is 50% gay because it involves at least 1 male actor; the amount of female actors is irrelevant. Gay porn is 100% gay because there are no counteracting (female) actors. Lesbian porn, on the other hand, is 0% gay because there are no male actors. Hence, yuri (by extension), is not gay.