Decades ago there was a UConn punt returner who was talking to the ref before the start of a game
He asked what type of hand movements would be considered a fair catch signal, and what hand movement would not, and also not penalized
And, as you might guess, during a return he made a hand motion of sorts that stopped the defense and ran for a td
More than likely the rules have been tighter since
edit:.... I believe I found it....
I remember the UConn player being interviewed afterwards and he said that the official said that wave was not considered a fair catch, thus legal.... the announcers were not aware of that during the game, and just thought the officials missed the signal