I don’t think people go through their days with the intention of “testing boundaries”. That’s just so unnatural and weird to even think about.
The more likely scenario is that they just have a habit of having that kind of sexual intercourse, and their previous partners either didn’t mind or didn’t bother mentioning anything, so they think it’s fine. When they run into someone like OP, it becomes a problem.
This is why feedback is important. No one is a mind reader. If OP didn’t give feedback, he would’ve gone and done the same thing to the next girl, which is morally worse than giving feedback even if you want to just block the guy without saying anything.