My first sensei was using me as an uke once. he requested a mune tsuki in the head but he was not happy with the way I did it. You could spot my attack miles away, and he told me about it previousely. It wasn't directed streight either. So, to make his point sink in my head he attacked me with a faster and linear mune tsuki, which would land on my jaw, I have no doubt, if I didn't block it.
We never spoke about the incident again, but I am sure each one understood what the other one was trying to say. I don't give away my attacks and he knows an opening may still be protected. But I have no doubt that he would hit me if I hadn't blocked it.
Some years later he started a new dojo and while there was no other students we used to fight. I think "brawl" would be a better word. No rules, but there were no full contact punches (he would tie me in a knot instead - a bit like in that joke - I saw fingers and decided to bite them but they appeared to be mine).
Those fights made me open my eyes to the reality of the fact that even putting someone into a pin may not be the end of a fight, that some people know a bit about Aikido and can escape techniques.
And I am still proud that out of those countless times I actually beat a nidan once or twice.