Just guessing

[Scrapper1]

Originally Posted by dbwill

In the mists of history (as a player in the 80's) we would judge the quality of an overhand set mostly by the spin - any side spin at all or more than 2* rotations front or back was a double.

In this neck of the woods, we're now being told that spin is irrelevant. You can apply spin just as easily with one hand or finger as you can with two hands, so that can't be a reliable criterion for judging a double. At least, that's what we're being told.