I can't for the life of me understand why you would separate sex acts by straight and gay, or by cis and trans, and so on. In the context provided, it seems like some sort of content warning when it's listed along phobias and triggers, as if homophobes and transphobes who want to play adult games would be using the system to filter it out. (If you can't handle the fact that gay and trans people exist, you shouldn't be using the internet.)
If its a searchable category and tied to adult games, it's going to be used for fetishization, (you even included 'fetish' as a category.) On a website that is home to many LGBT-friendly games, made by gay and trans creators, serving up different groups for users to consume for fetish purposes is weird and uncomfortable.
If I put aside my confusion, disdain and disgust at why you have separated these things, why you think gay sex is any different from straight sex and how you fail to see that trans people having sex would still be gay or straight, (because trans men are men and trans women are women, and trans is not a gender in itself, nor is intersex...) I still can't understand why there is a need or a reason in a content and age rating system to separate and label these things, as if it any of it would matter when deciding if a game is inappropriate before buying or playing. It seems like a lot of unnecessary information and not at all useful and I'm failing to understand why you would bother to separate and label it all like that in the first place.
If the main reason for a system like this is to keep children or teens from playing age-inappropriate games, it would matter if there was sex but not what kind. It's still sex. I just don't get it.