You have got to show me where you got this bit of information
Internet search shows nothing but I did read a book about the 22, the short was the first cased round made, the lr came later and gave the penetration needed to be a killing round many guns were made with 22lr. It was a common carry round before the media brain washed everyone into thinking only a cannon will do the job.
Like I said, I killed more critters were a lot scarier than any man I ever met all with a 22. Dropped 2000 lb animals right there one shot, now I am not saying a 45 wouldnt have done the trick but when meat is involed best not to waste much.
Would I consider a 22 for self defense? heck yeah, pin point accuracy and little noise, light recoil and fast back on target, sure would.