Basketball is pretty enmeshed with gambling, with college players, and a NBA ref going to jail over the years. The point spread is too easy to influence in basketball, heck I've been to games and the loudest cheer has been at the end of a game, when the home teams covers with some last second baskets.
But your point is right on, it's too easy to get at these replacement refs, and the NFL should be concerned.
And another reason why to be concerned is that most of the money lost was going to the Packers to cover, not Seattle. That means with the call, casinos, on-line betting, etc., weren't paying out, but instead, keeping the money. So that 150-250 million switch in action, was action that mostly stayed home with the house. Like the house needs the breaks....