First principle of VAR. Did onfield ref make the proverbial clear and obvious error? The answer to that is clear and obvious.
Stuart Burt, the AR, raised his flag after 13 seconds apparently as agreed over comms between the officials simply to signal the decision and mode of restart.
Fun fact: Oliver, Burt and the other AR, Dan Cook, together with Dazza England (of happy memory) regularly were a merry quartet who would spend free midweeks in the Middle East officiating the equivalent of L2 matches for a handsome stipend.