38 Super headspace is making my head spin

First topic message reminder :

All of the literature seems to blame the "accuracy" problems early in this cartridges' life, on the fact that chambers were cut to headspace on the semi-rim.  Doesn't the 38 Special, one of the most accurate cartridges we have,  headspace on the rim?  And wouldn't you think that headspacing on the rim actually gives you MORE precise positioning of the bullet relative to the beginning of the rifling, since we no longer have to worry about case length?  Why am I thinking that the Super should be, and have always been, a more accurate cartridge than anything that headspaces on the case mouth?

I wouldn't say it's about nothing. The question asks about 38 Super headspace - on the semi-rim or on the case mouth?

The prior posts in this thread indicate the case mouth. The OP suggests, based on the answer from SAAMI, that having it headspace on the case mouth could be dangerous. Well, what do we expect SAAMI to say? I'd expect them to say the same thing you would get if you asked a company about varying the reloading data they have in their loading manual. "Any deviation from what we publish could be hazardous."

But looking into the question a little further reveals something else. The answer is found very easily with a Google search.

https://en.wikipedia.org/wiki/.38_Super

Another article that looks at it as well:

https://www.ssusa.org/content/rimless-38-super-brass-everything-you-need-to-know/

Answer: It's okay to headspace on the case mouth, and most, if not all, guns do this now days.

A late observation: The original .38 ACP cartridge in the Colt 1900 and 1903 Pocket Hammer pistols headspaced well off the barrel hood recess because there was much more contact area available than on the later 1911 .38 Super barrel. Guessing almost twice as much! (If it's of interest I could measure the two.) I've also noticed the .38 ACP bullets in factory ammo used to be 0.359"-0.360" diameter up until the 1960s. Not all .38 ACP went to smaller bullets at the same time. Whether .38 Super bullets morphed in that time period, I don't know. I suppose I could check some Super barrels. One each from the 1930s, mid '40s, and, I think, 1950s. (The last might be late '40s.) None of those Colts are particularly well regulated to the sights, but they are about as accurate as your average 9x19 non-target pistol, i.e., 3-6" "group/pattern" at 25 yds.

The .38 ACPs were more accurate, even with the tiny sights, with vintage ammo when I shot them regularly about 25 years ago. Better triggers, too, which may have helped....

ETA: I'm not even sure that the real issue was "headspace" except as it relates to ignition uniformity and possibly "crooked" alignment of the cartridge in the chamber. At least, not like the headspace problems you consider with rifle cartridges, i.e. case head separation, light strikes and primer deformation that looks like high pressure, etc.