It's a dreadful rule. That Bromley thug, Bush should have been booked or even sent off for that challenge on Thomas. If he had been booked, he would have been sent off later in the game for a second yellow.
The worst example is the Pickford challenge on Van Dyke, which went unpunished;
It was an offside in this case, but why should it matter?
A foul is a foul, offside, throw in or free kick for an earlier offence, it shouldn't matter if the game is not in play. If someone commits a horrific challenge like Bush and Pickford did, they should receive a yellow or red card.