I don't find circle picking a particularly useful term because it means different things to some people and nothing to others, so I prefer to think about what's actually happening. Most of my picking is a wrist deviation and forearm rotation blend, with some thumb opposition/returning added on top depending on where I want the pick to be on the string. I think the thumb embellishments are where people get the circular idea, but moving the thumb alone isn't really an effective or sustainable way to pick. It's like an extra little push. Where I find a blend of all the motions useful is when I have to quickly double back to strings, like that descending two string lick. There's one note on the high E string for every three notes on the B string, so that's that fast little return to the E string for the one note each time. It might look like a preconceived strategy but it's just something that pops out when the maths of the lick demand it.