There's the letter of the law and the intent and spirit of the law.From my understanding, when they say "clear and obvious", they don't mean to a human official. They mean that if e.g. there's a foul then for the VAR to give it, it has to be very obvious that it's a foul rather than something up to interpretation. With offside, that doesn't really apply since it's objective - you're either on or off, however close it is. At the end of the day it's got to implement the rules, not decide whether they're good or not, and I think it got it right yesterday. If we don't like that then the rules have to be changed to allow a margin of error or some such, not expect the refs or VAR to adjudicate them however they like which'd be disastrous anyway.
The NFL went through all this with what is a catch and what isn't a catch the last few seasons. It basically broke the league in a lot of ways. This season they reverted to a more natural definition of a catch and it was better for fans, players and officials. Everyone "knows" what a catch is in the NFL.
We do not want to live in a world where goals are being called off because of a players nose being a centimeter offside. That's not the intent or purpose of the offside rule. If a video replay official can't tell in real time if a player is offside than it is not clear and obvious to me. It will absolutely ruin the game.