They blew that call. This is what 83.3 says:
“If, during the course of the delayed off-side, any member of the attacking team touches the puck, attempts to gain possession of a loose puck, forces the defending puck carrier further back into his own zone, or who is about to make physical contact with the defending puck carrier, the Linesman shall stop play for the off-side violation.”
If Makar doesn’t have “possession” of the puck, which is a ridiculous claim on its face and changes the conventional definition of possession in hockey, then he’s certainly attempting to gain possession of a loose puck while a teammate still hasn’t cleared the zone. Offsides. They missed that one.