What do you think is b_a_x_t_y’s technique here? It looks like wrist but also a bit of elbow.
I would agree, lots of DSX wrist but becoming predominately more elbow for long alternate picked single string type ideas
First impression is that this is quite similar to Vinnie Moore:
Primary elbow DSX (or wrist + elbow), plus a little forearm rotation for the “ascending inside” string change.
So this:
I had 2 lessons with him so far and we discussed his AP technique. Best lessons I ever had on AP. He knows exactly what he is doing.
I changed how I switch strings after the lessons and it is so good! Feels completely natural for me as a DWPS.
I don’t want to tell too much, but he is definitely DWPS.
He is switching strings more like Teemu.
I remember he posted a video about 2-note per string pentatonic licks and specifically mentioned he finds starting on an upstroke easier. This suggests a natural DSX motion.
Funnily enough, his most used patterns are nearly all USX (starting with a downstroke) so he’s great at both.
Actual mechanic seems to be a wrist + elbow combo (with elbow being more dominant at the higher tempos and longer passages. Almost like Petrucci in reverse.
I’m a bit confused by the use of the pickslanting terminology here, so he says he’s primary USX?
yes, downward pickslanting
DWPS =/= USX. Regardless, his pickslant looks more neutral to me, very similar to Andy Wood. If you look at his magnet footage he looks like he is primarily DSX but incorporating two-way pickslanting for mixed escape playing, again very similar to Andy 
Exactly my impression as well, that’s why I’m so confused 