Haven’t watched this clip before, but it’s clear he’s talking about the whole motion mechanic pickslanting connection. As we’ve discussed here quite a bit, there is a definitely a relationship between the pickslant, the way you contact the guitar, and the type of motion mechanic you use. The choices you make are all part of a system and we’ve seen how they correlate: uwps players like wrist, dwps players use rotation, and so forth.
For whatever reason Ben finds the pronated setup more comfortable, maybe because he hasn’t hit upon the same motion mechanic that @mcm is using, and they’re just different movements. Doesn’t mean supinated can’t also work, just means that he hasn’t figured out the movement for it yet. And those movements are indeed different.
Edit: Or at least can feel pretty different, based on lots of factors.