The downside to a uber-non resister is someone who falls down even before you do anything. That can be as frustrating as training with the uber-resister. Just putting some perspective... I'll leave and do some push-up or something at the little corner.
Funny, we have a young man in training now who is so very , very flexable that his ukemi is always unconnected and silly-looking.
Recently, after being encouraged to not be so concerned with trying to twiiiiiiisssssst out of everything, (resembling a contortionist) he has gone the other route and lately is just the sort of uke you have described.....finding his own balance in ukemi..
A fun young guy tho....just young.