and are included in CK2,

Also, fuck off PC Gamer, fucking awful journalism, literally just wanting hate clicks from the "well akcshually" fedora brigade.

OP is correct.

still existed

which is also why I'm happy with the separation of acts from inclinations.

why not add other existing but non-recognised sexualities to CK3?

Asexuality (negative spousal attraction penalties, -50% fertility, etc.) seems like something that's naturally balanced but perhaps this allows players to exploit gifting land to people who
will likely just die and give the land back to you. On the other hand, if done right, this could create really fun and dynamic scenarios akin to pushing genuinely reluctant royalty who entered monasteries out of the cloister to father children. This will probably involve tagging an ahistorically large number of people as "asexual" (using the modern definition) but I can see how it could lead to a lot of fun.

From a game mechanic point of view, I don't see how bisexuality adds anything. The risk is that it's a dominant strategy that deters people from choosing other paths. If you want to swing both ways, you can do so with the existing system that creates some mild penalties.