indeedLesbian sex is considered, purely from the porn point of view, straight; I'm certain most straight guys would rather see 2 girls than trans-on-male. Not shaming or trying to offend anyone, it's just how the porn categories go. As far as fetishes go, every person is free to watch (or do) whatever they like.
(to be fair, watching 2 guys go for it is also usually very arousing for women, so also that is straight, from the women porn point of view )