This is a complicated topic, and the chapter you’re commenting on was recorded several years back before we knew more about the motions, like we do now. So I apologize!
Basically, when we first “discovered” two-way pickslanting, we noticed it because there as a sudden arm motion at the moment of the switch. So we thought, ok, that arm motion is what two-way pickslanting is. I started practicing this, got good at it, and so we thought, ok, this works. That’s why we started teaching it that way, and that’s why Chapter 8 is called “down, up, rotate”:
https://troygrady.com/seminars/antigravity/chapter-8-down-up-rotate/
So yes, in that particular way of doing things, the “rotate” movement is accomplished by a combination of wrist and arm adjustment. The Pickslanting Primer goes into a little more detail on the arm and hand changes necessary to do this. You can check out this page. The Chapters are pretty short. I’d just watch them in order:
https://troygrady.com/primer/two-way-pickslanting/michael-angelo-batio/
Now here comes the “gotcha”. After a few more years of doing interviews, we discovered there are players who can do these same types of lines with no (or very little) arm movement at all. Here’s Andy Wood playing the ascending sixes pattern. When he speeds up, the arm movement is almost non-existent:
https://troygrady.com/interviews/andy-wood-workshop/electric-clips/ascending-sixes-positions/
So we then realized that there is a more general meaning of “two-way” pickslanting. It means when you have two different picking motions, and you use one of those motions for the downstrokes and the other one for the upstrokes. And it doesn’t matter what type of arm or hand motion you use for that, and that you can do it with only pure wrist motion and still get a similar result. The pick doesn’t “rotate” any more in the pure wrist version of the movement. But it definitely does trace a curve, same as the arrows we draw on the screen in the Pickslanting Primer.
The final piece of this was realizing, hilariously, that not only are there players out there that do this, but I myself am one of those players! If you compare the descending sixes example from years ago in Antigravity, with the same example more recently in the Pickslanting Primer, you will see the difference:
https://troygrady.com/seminars/antigravity/clips/first-sixes/
https://troygrady.com/primer/two-way-pickslanting/michael-angelo-batio/clips/descending-6-the-scale-chunk/
The Antigravity example uses a more vertical pick path, so there needs to be more arm turning when you do the string changes. The Pickslanting Primer example uses a flatter picking path to begin with, so less arm turning is necessary. It’s almost completely gone, but not quite. Same principle in both cases. What was clearly happening over the several year gap in between, is that I was learning how different wrist movements work. I didn’t get all the way to “Andy Wood” land of mostly wrist and no arm until recently.
So where does this leave you? What this means is that there are different ways to achieve the same or similar result. The Antigravity method of two-way pickslanting uses a supinated arm, a more vertical picking motion with the wrist, and some arm turning at the point of the string change. The Pickslanting Primer is similar, just flatter. And the Andy Wood version of things uses the flattest picking motion, and very little to no arm turning most of the time. All these methods work, and you can practice any of them.
If you want to try the Antigravity style, you can watch Antigravity, and also the Pickslanting Primer which goes into a little more detail on how to do the wrist and arm adjustments when you make the string change.
If you want to try the Andy Wood style, I recommend the recent “Crosspicking With The Wrist” broadcast, which explains how he is able to switch between two different wrist movements:
https://troygrady.com/channels/talking-the-code/crosspicking-with-the-wrist/
So yes, the movements can be the same between “crosspicking” and “two-way pickslanting”. These are more descriptions of alternate picking styles rather than movements. And again, I apologize for that confusion. Try not to worry about the terms right now. Just worry about the hand movements and you’ll be good.
Let me know if that helps clarify.