sean has a very distinctive drum programming style. he can pick up a drum machine and make it sound like him, if that makes sense. his style sounds hip-hop influenced, but with a very clipped, almost militaristic feel to it. he's got his own unique sense of timing. robs got a looser, funkier feel to his stuff, much more improv based. you really get a sense of how they interact listening to their concert bootlegs (esp. the untilted & quaristice tour stuff).
of course, i have no way of knowing for sure how this track was done. maybe it was a jam the 2 of them did, maybe it was sean intentionally trying to do a rob-style track, who knows. just from an initial listen, my first impression was that this sounds more like rob.
on one hand, i don't like disecting this stuff. i like the 'autechre' mystique and the sense of mystery behind it. on the other hand, the fanboy in me can't help but want to peek under the hood a little bit and figure out how this stuff is made.
I also had the impression that the last time I saw them live sean is very much into wild insane drums while rob is more into melodies. Sure its too easy to just nail it like this but its interesting that you had the same impression of this tendency.
I always wonder if Quaristice is more Seans work while Oversteps is more Robs work. (not in total but who was the main influence or who kind of took the lead in the project) I would definitively play with these things if I was them.