I din't read this thread, but have read a few others on this topic over the years, and seen the tiny bit of video evidence that is out there for a slip stroke from 1950.
Maybe it wasn't even really a technique? Maybe the hand was just moving around a bit to get settled in during the practice swings.
It sure seems dumb to intentionally leave the stick in place at the cb, then slip the hand back several inches to a foot, then squeeze the cue on the final forward stroke and strike the ball. The stick has no momentum in that case, and only the hand does, picking up the stick for the ride.