The beer bottle case is explained in the article: "Take a beer bottle or an upturned glass and send it spinning down a table: if it rotates to the right, clockwise, it will curl to the left; if it rotates to the left, it will curl to the right. That’s because the bottle, as it moves forward, also tips forward slightly, adding weight to the leading edge. More weight means more friction."

I guess a heavy curling stone with a lower center of gravity and on a slippery surface would'nt tilt forward like a bottle.

Came back to this thread to see if someone had written an enlightening rebuttal of GP rather than downvoting him.