For most people, it means going to about 10:30 or 11:00 oclock on the "swing clock". Certainly, not every person is going to have the flexibility and/or athletic ability to go back that far. On top of that, a lot of people may not have the golf ability to go back that far and control their swing on the forward swing.

But, physiologically, you can't have a conventional grip in a golf club, and keep it on plane, and not rotate it and take the club back to 10:30-11:00. Humans just aren't built that way.