bobmac
Major Champion
The Rules say nothing of the sort. The Rules do not define a practice swing.
The Rules do not define a practice stroke. They do of course define a stroke, unqualified by any other word. The definition includes an intent to hit a ball.
Some golfers are confused as to the difference between a practice swing and a practice stroke, neither of which appear in the Definitions section of the Rules book. The main feature of apractice swing is that there is no intention by the player to move any ball. It occurs when a player simulates a stroke, usually in preparation for making one. It may also be used as a loosening-up or training exercise while waiting to play. Conversely, a practice stroke is made with the intention of striking at and moving a ball, even if it is a plastic ball (ie it is a stroke by definition).
I'm losing the will to live, I'm out.