Generally it is one of familiarity. Goalies have routinely been allowed to be late as fuck and as long as the attacker was able to get their shot off they are not be penalized. There is no justifiction in the rules for it, other than just a collective understanding that we let goalies do it.
It’s largely indistinguishable though from what Silva just did on Saka to justifiably get his yellow card.
But for that terrible offside decision against Brentford, I think Arsenal would take a draw here. Getting to the other side of City’s best chance to close the gap with a 5 point gap would have been significant.