I disagree because the pianist either plays a score or otherwise decides what to play (e.g. improvisation) as distinct from generative elements. I only have a sketchy understanding of how Max works but as I understand it you can use it to trigger musical events within defined parameters and then refine the parameters to produce more desirable results. I would assume Sean & Rob construct parts with instructions like "play notes in this scale within these rhythmic limitations" or "play combinations of these six notes" and apply conditions and exceptions. Or maybe they invent a melody or chord sequence and have randomized (but controllable) things happening to it or against it.
Edit: and I know they've mentioned using "if A then B" type commands
My overall point being that it's a different method of composition / performance than sitting down at the old joanna, "Seinfeld voice" not that there's anything wrong with that. One of the most revealing comments they've made about their process, I think, is comparing it to jazz, though it's (as I understand it) generative factors (controlled, to varying extents, beforehand or in real time, by them) that are producing the variations, rather than the decisions (also dependent on parameters) that go into a jazz solo.
Also think of Cage and others expanding the parameters of the piano with prepared piano techniques, e.g. using objects to damp the strings or change the timbre - there's a direct lineage from that to the way our bois mess with the envelope