I think the argument is that if Oliver says:Ok but then what's the point of VAR if it can't ask a ref to review their own decision. If that's the case then the pitch side monitors will essentially never be used again ? Seems an odd decision by Webb. But also in Brighton vs Spurs Webb had to apologise to Brighton for the mistakes. Again this doesn't make sense to me.
De Bruyne didn't ever have the ball in his control/possession. Which is true.
Partey gets to the ball first. That's also true - he probably could have played it, but decided to block and let Ramsdale collect.
Partey gets between De Bruyne and the ball. Whilst there's a lot of contact between both players in the end, initially he does plant his foot down and Kev kicks into it first.
Clearly if Kev was running with the ball, or had already played it, then it would be much more likely to go City's way, but if Oliver has seen all that and has decided that Partey gets there first and is blocking Kev, then VAR can't do much about it, as he's seen it.
If he'd given a pen, that almost certainly wouldn't be overturned either.