There's a difference between slip stroke in reference to Mosconi and slip stroke as is most commonly referred.
The way we use the word today, slip stroke involves the sliding of the cue through the grip hand on the follow through.
Mosconi's slip stroke was a sliding of the cue through the grip hand on the backstroke.
wrong!!
This has always been the definition and always will be "sliding of the cue through the grip hand on the backstroke"