I certainly understood the concept of the captive nut and its function, it was just one of those situations where the theory didn't reflect the reality.
I loosened the captive nut OK, but trying to wind it off to withdraw the flywheel just distorted the flywheel (as others have found).
I figured that if I positioned the nut halfway through its "free travel" (between where it is pushing down on the cam collar, and pulling up on the flywheel) that I could use a puller to break the seal of the cam collar on the crankshaft taper, but it wouldn't budge. I built a series of heavy steel jigs to fit into my shop press, but none worked.
Eventually I resorted to drilling out the rivets that hold the bronze flywheel to the steel cam collar, which left me with the following....
