I know some referees who think that way. The player had to make some attempt to get over the tackle, it's not enough just to see a leg and then pretend to fall over it. As Stan Collymore said, the player has to be prevented from doing what they intended to do. The worst case I ever had of players trying the 'sneaky stuff' involved ex-professionals, which was rather disappointing. It's supposed to be a sport, not a con-trick.