Yep then they review the call to make sure it is right.It's really a stupid rule then even if it's called correctly. I assume the whole point is so you don't trick the other team, but as you can see in that video NW was still going full steam ahead becuase everyone knows it wasn't a fair catch signal. I will say that overturning that one is alot worse than DeJean today.
One other point, it does appear Minnesota might have let up a little, but that has no bearing on anything. Plays like thay happen all the time, especially where the ref can't figure out if it's a forward or backward pass, then the other team runs it in for a TD while the other team is standing around.
If it is found to be a backward pass, they let it stand, if it was not they negate it. This happens all the time, they let plays, play out then review to make sure it is right. In this case it was not. So....called back.
The rule is the rule and its been that way for many years.