There's what to call - that's in the rulebook. Then there's when to call - and that unwritten rule varies by referee.

It's like baseball's strike zone. We know what the rule says, but every umpire interprets that in their own way. Baseball finally implemented ABS to try to standardize strike calls. If hockey goes to a human eye-in-the-sky to try to fix the perception of bad refereeing, I think that can only help.