If you watch Jazz guitarist Martin Taylor, you will see he anchors his pinky to the scratchplate. However, he does state on one of his instructional videos, that it was a "bad" habit he picked up when he started playing, and that you should'nt really do this if you can help it.
Its the thing about guitarists - What one finds helpfull, it is not so helpfull to another. People set down guidlines, but not everybody is suited to these rules.
Its been proved over and over again with famous guitarists.