This is a pretty “inside baseball” question for which you shouldn’t apologize because all it does is show you really get the concepts!
If you look at players like Andy Wood, he doesn’t appear ot have any sort of continuous USX motion. He’s basically a DSX player who occasionally uses double escape motions for doing what you’re describing. Which btw is what we’re calling that now. The term “crosspicking” just confused everyone because it means multiple things. But double escape pickstroke only means one thing — a semicircular pickstroke type.
Now, keep in mind, there is a complexity here because there are multiple ways of making a double escape pickstroke, and Andy uses both ways. The more obvious one involves a combination of wrist motion and forearm motion. That’s the one you can see where the arm is flip-flopping around. And it’s what we used to call “two way pickslanting”, and what we refer to as “down up rotate” in the lessons. But you can do the same thing with no arm motion at all, in a way I would not really describe as “down up rotate” or even “two way pickslanting”. That’s what Andy is doing here as he speeds up this sixes pattern:
In the third and fourth repetitions, there is no “rotate” or change in “pickslant”, and yet he gets over the string just fine, simply by changing the direction his wrist is going. This is why in the new Pickslanting Primer wrist motion updates, we don’t teach “down up rotate”. We just teach the two wrist motions — USX and DSX — with the implication that you’ll just flip flop between them to do whatever string change you need to do.
As you’re pointing out, this still technically creates a “double escape” pickstroke right at the switchover point, but that’s not really what it feels like to do it. It just feels like making downstrokes and upstrokes, honestly. This is why players like Andy have no notion of using two different wrist motions. And I also wouldn’t really call what Andy is doing here “two way pickslanting” since there is no change in pickslant for this. Again, it’s just a change in wrist motion.
So, the answer to your question is no, not all players have both continuous DSX and USX picking motions. They might have one of them as a default, like Andy does. For licks that require both escapes, they may briefly use a different wrist or arm motion, but these brief motions are generally just used for the string change, and they don’t appear to be motions they know how to make continuously.