So we have refs making subjective calls in the moment about whether something is or isn't a penalty / red card etc etc.
We then have another ref applying a subjective view to see if the first decision is correct.
We then have the same other ref making a subjective call as to whether something crosses an undefined (undefinable?) threshold into being "clear and obvious or not".
I don't get why a threshold is needed for something which is important and has such an influential impact on a game, a tiny mistake is still a mistake. Having a process that acknowledges a mistake, but it's only a small mistake so we'll stand by the mistake just seems odd. I'd much prefer that things like penalties, red cards etc are correct. WRT off-sides I'd regard a toe-nail / armpit etc as being trivial, but I'm not sure how that would be codified.
Imho "clear and obvious" should only apply to things which tend to be more trivial, but then VAR doesn't tend to get involved in those anyway.