Tim and Goetz,
I don't feel taking ukemi is a good way to determine someone's ability per se, as it may still cooperative to some degree. This isn't difficult to understand. Why are brand new beginners hard to throw? They don't "move right". They haven't been taught how they are supposed to move so they can fall down, ie cooperate.
There's no need to get dramatic about this. By definition, uncooperative --- 1: unwilling to cooperate; 2: intentionally unaccommodating;
This doesn't have to be a fight to the death, it simply means what it says, someone is intentionally unaccommadating, and there are numerous safe, effective ways of doing this. Wrestlers call this "wrestling". Judo refers to this as "randori". BJJ calls this "rolling". Boxers say "boxing" or "sparring". Tomiki folks are quite familiar with this type of dynamic training and to the best of my knowledge also use the term "randori". I suspect you both know very well what I'm refering to and are being deliberately obtuse.