When Hammer fucks Myriam, she deliberately stops him from fucking her pussy, instead taking it in the ass. And she says at the time, that would really mess her up. Zorlun is pretty much making it clear, it's not a good idea for Hammer to fuck Myriam's pussy. So this idea that it's a fantasy and therefore anything can happen, isn't matched by what Zorlun has actually done. If he'd done the opposite, then maybe you'd have a point. But he didn't. And the logical conclusion of that, is that he wants most of the game, to actually bear some relation to reality.
We have a section of the game, where Zorlun can totally indulge his creative craziness. And then we have the rest of the game, where things generally follow a realistic course.