Decoding Josh Meaders picking

Really curious what people make of Josh’s technique. At 4:55 you get a pretty good view of his right hand as he plays these fast lines

From taking a lesson with him I know he does Down, Up, Hammer/Pull for 3nps, which makes sense for a traditional USX style + sweeping. But what’s confusing is he also says he does 4nps as D, U, D, Hammer, which would make it much harder than just pure alternate?

I feel like I am also seeing some DSX and mixed escape semi circular motion as well throughout the video. Curious what y’all make of his technique here!