People who don't have a good 1hbh form always talk about 'extreme' grips.
Most of the people mentioned here do not have extreme grips. They are on the conservative side. I define the grip by the knuckle and not the heel pad. These players have small grip sizes. Stan, fed, haas, youzhny, dimitrov all have conservative grips. The knuckle is on the top bevel and in most cases heading towards the first bevel. Youzhny's grip is almost continental. Their 'look' and spin come from wrist control and supination and swing path. A conservative grip allows you to 'whip' it more. Henin's grip is more extreme than avg because she was short. Find a good clear pic of these players and you'll see their knuckle is not on bevel 8 or even the edge. They are getting power from shoulder usage and the swing is more of a 'lift'. a lifting up of the arm. not a 'push' from the palm.
if you look at the wrist and top part of the forearm there is usually no wedge there. their wrist is pointed down (usually). there's a flat line between upper arm and the top of the wrist. they are pointing the wrist down to create the angle.
edit: I see Borami is saying the same thing. He is correct.