You can conjure up as many excuses as you want IC-ly, it doesn't change the fact it's there to push an agenda.
Also, just because something "can" happen, it doesn't mean it SHOULD happen - that's the big exclamation mark here. Especially in a video game. All of this is just there to rake in points from the LGBTQ people and their supporters.
It doesn't make even a flick of sense otherwise. Flynn and Shaw? Like, WHY? Not to mention that the transgender Kyrian wouldn't be a big deal if he was just there and we get their story in a side quest or something, instead Wowhead and several other blogs on the web made posts about the "FIRST TRANSGENDER CHARACTER TO JOIN WOW WOOOO". And this is exactly what Blizzard want by ticking those boxes.
Not to mention Blizzard changed calling them "they" to "he" after LGBTQ folk insisted on it, and made a post about that as well.