I think they're confusing a practice swing with hitting a practice shot during the round. The rules are specific about that. You ARE allowed to practice chipping and putting (around the tee box while waiting for the group ahead for instance), you are NOT allowed to practice FULL shots (i.e actually hitting a ball with a full swing). I could look uo the rule but so can you.

I can't imagine not being allowed to take a practice swing just before addressing the ball. Don't your friends watch Tiger Woods? He always goes through a quick couple of practice swings to get the feel for the shot is is about to play.

Practice (Rule 7) is allowed as follows:
1. Before or between rounds, a player may practice on the course.
2. During the round, a player shall not practice either during the play of a hole or between the play of two holes, except that, between play of two holes, the player may practice putting or chipping on or near the putting green of the last hole played, any practice putting green or the teeing ground of the next hole to be played in the round, provided such practice stroke is not played from a hazard and does not unduly delay play. Strokes played in continuing the play of a hole, the result in which has been decided, are not practice strokes.

J