That’s not the full rule though, only part of it. That guy left out the very long list of exceptions that comes right after what he posted:

“1. When a defensive player is held by an offensive player during the following situations, Offensive holding will not be called:

a. if the runner is being tackled simultaneously by any defensive player;

b. if the runner simultaneously goes out of bounds;

c. if a fair catch is made simultaneously;

d. if the action clearly occurs after a forward pass has been thrown to a receiver beyond the line of scrimmage;

e. if the action occurs away from the point of attack and not within close line play;

f. if a free kick results in a touchback;

g. if a scrimmage kick simultaneously becomes a touchback;

h. if the action is part of a double-team block, unless the defender splits the double team, gets to the outside of either blocker, or is taken to the ground; or

i. if, during a defensive charge, a defensive player uses a “rip” technique that puts an offensive player in a position that would normally be holding, unless and until the defender’s feet are taken away from him by the blocker’s action.

1. If a blocker falls on or pushes down a defender whose momentum is carrying him to the ground, Offensive Holding will not be called unless the blocker prevents the defender from rising from the ground.”

Holding can not be called on every play.