So i found this video of guthrie
At 2:25 he starts to talk about right hand picking.
He seems to be explaining forearm rotation but then demonstrates what appears to me to be wrist motion with a hint of elbow picking only later to go back to forearm motion when explaining the funk style.
Just reinforces that a lot of these giants must be doing this by feel as they seem unaware of the differences between right hand motions the way the CTC community are 
The faster funk stuff actually looks like wrist motion to me, more like a 2 o’clock or even 1 o’clock motion, just done from a flexed orientation:
The frame rate fails us here — if this was done in Europe it may have been originally shot at 25p which is even more blurry with worse rolling shutter than 29.97 video. And of course he’s playing very fast. But in general although there is probably a small amount of forearm, I think you can see that what’s really going on is the hand itself moving along a reverse dart thrower trajectory, again, like a 2 or 1 o’clock pathway. I think it’s similar to what Andy is doing here:
It sure s has the same look as andy’s
Which in turn is similar to this by Paul Gilbert.