[Seanmx]

I believe it was Clampett who made the comment about a difference. Maybe the US Tour does play under a Local Rule. A Google search for "Mickelson and embedded ball "produced several references to news articles. Here is one of them-

"It was an adventuresome second round which featured an interesting ruling on the second hole where Mickelson had to take a penalty stroke for relief from an embedded lie in a sand dune. That's different than the American rule allowing a drop from an embedded lie. Here, a free drop is granted only if a ball is embedded in a mown area.

The ball rolled forward after two drops and several more attempts to place the ball. Finally, when the ball was deemed to have been properly placed, Mickelson left the area to make his club selection. That's when the ball started rolling again to the fringe of the green and an official ruled the ball in play. Mickelson two-putted for bogey 5.

"Fifty-one weeks out of the year it includes the whole golf course and this week it's got to be just the closely mown areas," Mickelson said."

I think that’s a local rule on the US tour.