I’m sure Atkinson told him VAR had ruled it offside, so raise the flag so everyone knows it. I did notice it was quick decision and the view shown in TV had the ball about a foot away from the head of the header, so the “timing” of the stop motion was completely bogus! But then, the FA have already had to admit they don’t have the ability to stop the play at the exact moment these things occur and have to use their best guess as the correct frame to use...and then rule on matters by fractions that are smaller than the timing could possibly take into account!
What a joke system!
Over here, they showed the replay, SAID he managed to stay onside, then had to just gloss over the fact that VAR was simply a fleece job!