I have been shooting neck sized(Lee collet die) Lee factory crimped loads in a 30-06 bolt action as my standard hunting load for a couple of years. I tried all sorts of seating depths with out a crimp and found loads crimped into the cannelure of a Hornady bullet gave me better accuracy with a number of loads. BTW, no problems with neck sized cases with feeding or extracting. I am convinced that the factory crimp makes one's loads less sensitive to many variables just like Lee claims. That makes load development much easier and more straight forward. I am an engineer and my analysis of my shooting statistics bears this out.
CW, you are obviously a reloader of considerable experience and refined technique. You are exactly tight about the issue being neck tension. I guess the FCD is a lazy man's way to control it. That is why I love it.