I tended to think what was meant was that the grip was just strong enough and in the right spot to trigger the pressure point for yonkyo which would not be that hard to do by mistake in that grab.. Maybe I am wrong and the OP meant that it was intentional in which case I would be having a serious private chat with my teacher about the issue to insure that he was aware of the situation and would pay attention and intervene when he sees it happening. And I know my teachers well enough to know that they would not stand for that sort of behavior in the dojo.
At this point if someone were
intentionally doing that to me ( and I was sure it was intentional) I would not put up with it. And if the continued to disregard my requests for proper ukemi after sensei had a chat with him, I would probably do something not so nice about it until he got the point.
Another thought to add is that at 3kyu (in my dojo) one can start doing techniques less static and in motion and you don't have to wait until the grab is on before you move into the technique.