When I read Maryen's route for the first time, I didn't look at the walkthrough in this scene, I just chose the way I would have done it in reality. And that's why I didn't pay attention to this important detail. Yesterday I gave it importance and thought about it even more.
Further events confirm my assumptions, especially this scene, when Maryen urgently needed to discharge her arousal in Homaspernia, without the control of Evalin (the nun-demon)
I have already noted before that giantesses seem to have a latent desire (maybe not for everyone) to crush objects using their body and its weight, dominate the tiny. And it is not about corruption at all, you can see it in Regina's example. And they may have dogmas, but they are not able to fully contain their hidden desires, which are almost necessary.