From some of your other posts on here I am thinking you are probably just a troll, but I'll respond anyway for the sake of anyone else reading this in the future. To the overall points anyway; don't care enough to bother with the ad-hominem junk, this ain't about me.
When it comes to nsfw games, as in porn games, generally they're going to put a picture of a girl up front if it's for people attracted to girls, and a picture of a guy up front if it's for people attracted to guys. If they put multiple characters on, then you can sometimes narrow things down further depending on how they are posed; they could be together, or they could be different options. Also, justified or not, the target audience of any sort of porn tends to be men, even if the actual audience is much more varied. The end result is: if you see a male character on a porn game's title card (and especially if you see two or more male characters together), it's probably gonna be gay, and if you see a female character and in many cases even if you see multiple female characters, it's probably straight, though lesbian is still a possibility, especially on this site. Yes I know the latter half is half of what you are objecting to, please don't hyperfixate on just that.
If we were talking about actually safe for work games, that's a different story. Nothing wrong with lgbt characters showing up, or being in romantic relationships on screen, I fully support that. Plenty of awesome characters out there who happen to be romantically/physically attracted to their own gender as just one of their many character traits. Being openly out there and having representation is outright vital, not just for public support to acknowledge and accept it as normal, but so gay people don't have to deal with random police raids and shit like in the bad old pre-Stonewall-riot days. But we aren't talking about safe for work games, we are currently talking about porn.
In the sort of games being discussed here, the characters are doing a whole lot more than just EXISTING. Doing a lot more than even just kissing each other, too. They are having sex with each other, explicitly, on screen. Often, that is like 90% of the game's content; just the characters having sex. Nothing wrong with that, but depending on the genitals of the characters, not everyone is going to want to see it. In circumstances like these, male-on-male, female-on-female, and yes female-on-male as well, are all basically just fetishes, no different from stuff like bdsm or ntr or vore or poop or whatever. Some people will be into it, a lot of others will be outright grossed out by the sight of it. It is the responsibility of porn makers to properly tag the fetishes within the porn that they are making. And, more relevantly to this overall thread: it is the responsibility of the hosting site to make it so people can actually properly filter using those tags, and itch.io is failing in that responsibility.