Because if the ref had been asked to go and look it on the monitor - how would he have not given it. He would have had to hand back the brown envelope surely? So - better not refer him to the monitor.
Re-watching the highlights - the lino when flagging the Mitoma goal actually keeps patting the PL badge on his upper sleeve showing where it hit. ie: not handball according to the current rules.
Not entirely made up by TV
https://www.premierleague.com/news/1820123
The other thing - if it had hit MacAllisters thigh and gone in - would he have been given the goal, or would it have been Welbecks? Because if it had been Welbecks - then MacAllister didn't 'score' with his arm.
In fact I have even more admiration for our players. If that had been me out there I would have blown my top, and would have been sent off. They kept their calm remarkably well I thought.