Short-Barreled Rifles (SBRs) are handy, easy to carry, and reasonably accurate inside 200 yards. They’re also a huge pain in the butt because they are (absurdly) regulated under the National Firearms Act, and carry with them an inordinate amount of bureaucratic aggravation.
Pistols, however, are not regulated under the NFA, and it is legal to mount a stabilizing brace on pistols, and then use that brace in the manner that Yeager (and virtually everyone else) does, as a short stock.
It is a blatant work-around of an absurd law? Absolutely. Is it practical? A lot of people seem to think so.