It doesn’t really apply to this but just another form of timestretching where you loop grains of the sample then move the start point.
A loop mode which would behave like the default pingpong grains in ableton.
IE when it reaches the “end” instead of looping from the start, it now plays in reverse.
Then when it reaches the start again it plays forward again.
This bouncing back and forth would reduce artefacts that can appear when you are rapidly restarting a sample when looping!