This is the key angle which confirmed the offside decision on West Brom's second "goal".
— Dale Johnson (@DaleJohnsonESPN) May 16, 2021
Matt Phillips is stood in front of Alisson in an offside position blocking his line of vision to the ball. Nothing else is relevant.
If this were allowed, teams would do it all the time. pic.twitter.com/ClmxpEHyUd