Prior to this, I would have said that this type of Uke was "incorrect" as it was not "responsive" in the nature of a "real attack".
You are correct that it is a challenge. It represents what I consider to be a huge difference. Many might interpret it as not being a "true attack" or "true pressure" therefore, invalidating the "reality" of our art.
Communicating and understaning the difference in this way of training is going to be a challenge. My partner and I had to be reminded many times that we were not doing it correct over the weekend!
Great points. I think a lot of people mistake what's going on during class as scenario based training as opposed to lessons to get glimpses at some deeper more fundamental truths/lessons. I did a one night guest instructor thing recently at a local Aikido dojo and we were working a very slow systematic cross hand grab kotegaeshi. One student called me over to ask about the ukemi. He asked if he should be grabbing and yanking, or grabbing and pushing or grabbing so that he could sucker-punch or kick nage. I responded that he might just grab as if it was an exercise in Aikido class and try to connect to his partner's center through the grab. No momentum, no tricks, just solid physical connection so that nage could really see when what he was doing worked, and when he had nothing. That's surprisingly hard for most folks (in my experience anyway).
I wasn't there for Mike's seminar, so hopefully that's along the lines of what you were saying. If not, apologies for the misunderstanding.