I guess on both sides they start out as star -> collapse, but one either side the collapse continues into a hole. Within those parameters the star will stop collapsing and go supernova and never collapse back. I guess that's what it means.

Yes, this most likely just means that different processes are responsible for the same outcome (i.e. becoming a blackhole), depending on the mass of the star.

Edit: see https://en.wikipedia.org/wiki/Pair-instability_supernova#250...