I have encountered a situation where I misclicked on my turn, forgot that there's an undo feature, passed the turn and then said something about it in the chat just for small talk, and my opponent suggested that we could undo it, but since he had already played cards (which were not really relevant to the "decision" I made, anyway), I declined since I didn't think it would have been appropriate to undo after getting that new information of seeing the cards he played.
So yeah, I totally wouldn't have granted that undo.