To clarify, "headspace" is usually one word. I think you maybe caused confusion with the character space between "head" and "space" in your previous post.
I agree about headspacing lead on the bullet though. It has significantly accuracy advantage with every lead bullet load I've tried. It also seems to reduce leading. It doesn't seem to do much for jacketed bullets, but I suspect a lot of those are unseated by the primer before the powder gets up to speed, so they wind up fitting themselves to the throat. Lead bullets aren't hard enough to do that without distorting.
Headspacing on the extractor of 1911's is common. Many are loose enough and long enough in the chamber to do that. Headspacing on the case mouth was Browning's intention, but some think as few a 30% of 1911's actually do that before the extractor hook gets hold of the rim to become the defactor headspace determinant. I can't speak to the other makes.
If you go back and look at the roll-crimped rounds used by the old time match shooters (and a few modern ones), they generally allow the leading edge of the lead bullet to protrude beyond the case mouth at least 0.020" and often more. That means the cartridge actually headspaces on the bullet when it finds the throat, so the case never goes deep enough to jam the case mouth into the throat. The roll crimp does increase start pressure and consistency, but wears your cases out faster.
The taper crimp, set to dig just slightly into a lead bullet, will still leave enough mouth width for case mouth headspacing with most case brands, assuming the chamber's extractor hook doesn't stop cartridge forward insertion first. It does protect against a lubricated lead bullets getting pushed into the case (setback) while going up the loading ramp, though. That's not usually a concern with unlubed jacketed bullets because of their higher friction with brass.
