This is a fascinating discussion. I basically find myself agreeing with Jim Vance's perspective and most of the thoughts I've had have been brought up by him at one pont or another. However, there was one thing that I thought I might add.
There are people in my dojo whom I can peg with a shomen (or munetski or whatever) in standard 'kata' training every single time if I want. My timing is just that much better than theirs. There are also people who seem to be able to peg me any time they choose because their timing is so much better than mine. Similarly, there are people who couldn't 'deny me ikkyo' no matter how motivated they were and hoy much information they had, and other people who seeem to be able to turn me into a rag doll any time they choose.
So, I guess I'm saying that my experience of learning proper timing through kata is that it certainly has taught me skills that I notice, and that I still feel that there is a lot that it has to teach me.
I think the turning in a stopped car analogy, by the way, is probably not reasonable. The stopped car is more like making the claim that there is no timing if you are practicing static technique (first uke grabs and only after uke has grabbed does nage start moving). I think kata is more like practicing turns in the parking lot before you go out into traffic.