I couldn't say where our host draws the line, but I'm one of those people who uses itch.io in SFW mode even though I would much prefer to see NSFW material. That's because a lot of the "mature" games people post here are just gross instead. It's a common problem across social media, and the reason IMO is that a simple "tame/mature/adult" ranking is simply too coarse. Does it involve nudity? Is it sexualized? Or are we talking someone pushing their weird fetish onto everyone else with little to no warning? But for some reason no online platform goes into that kind of detail, and games like yours suffer through no fault of your own.
Edit: not to mention people in certain countries consider healthy issues like sexual orientation to be NSFW...