He did and that's why Gakpo stopped but I think the point is that if Gakpo had pretended not to hear the whistle and scored then what would Taylor have done? I can think of a little Uruguayan that would have smashed that one in and taken the risk of a yellow.
The rules state that when the whistle goes, the ball is dead, so had Gakpo kicked the ball and scored, it would not have counted.
That's not the issue here at all.
The issue here was and still is why he whistled in the first place. Either he's signalled "play on, no foul" or "foul, but advantage" when Aerola went up for the ball.
Play on: He has no grounds to stop play if Areola doesn't clearly signal that he requires assistance or another player doesn't draw his attention to a serious injury.
Advantage: He can blow the whistle if he considers that there was a foul (though he didn't signal one at any point), or if he saw there was a foul but WH retained control of the ball initially, but then no advantage accrued. While I suppose he could argue that no advantage accrued, he'd be hard pressed to justify it as everyone gave the GK space and the GK then casually rolled the ball in front of himself.
However, as he gave a drop ball to restart the game, he's signalling that he didn't consider that the break in play was due to a foul, only a stoppage for injury.
Areola thinking that it was a kick-out or a free kick is not grounds to blow the whistle.
So, by elimination, he's blown the whistle because he sees that Areola thinks it's a free kick, realised he shouldn't have, and fabricated the injury instead.
It may have been an honest mistake, but it's a huge one.
