NFL "football move"

[emceemc]

I saw a receiver make a fine catch in a bad weather game. He catches the ball with both hands as he slides a full 5 yards on his shoulder to the side line. He never makes any attempt to tuck the ball, run, or anything else. He purposely remained still to avoid losing the ball. There is no "football move" there. Nor is there a football move in many sideline catches. Nor is there a football move in many mid-field or end-zone plays. The rule seems to be a football move is not required unless the ball is dropped. Is a football move required to complete a catch or not? And doesn't the rule, whatever it is, just force the referee into a difficult and unnecesary judgement call?