@jwelsh - I'd go specifically with "Ambient Jam." Much more so than any of the other secret sets.

@chopcg - sign'd - also a huge proponent of "aimless noodling" for the exact reasons you state.

@bertoletdown - "one big idea" - I believe that captures many of the big jams of the fall. More than a handful of them really boil down to a very simple two chord pattern as a foundation, but with everyone so deep in the pocket that it is hard to comprehend how deep and involved and all-encompassing they are. Like, you can get submerged or surrounded in them.
Particularly with the first half of the AC Twist, it comes across as more involved than that, as the music comes across as a full band call and response exercise - almost like its two different full bands yelling back and forth at each other. Starting to evolve a little after 10 mins, and developing in through some hey-hole woos (11:20) and really picking up steam from there.
Listening again, they integrate the Get Back tease with the music that comes immediately after it. Like they have a cross-fader going every 4 measures til Under Pressure emerges (directly out of the left channel, call it) and starts spinning on the third deck around 13:40.
Its fucking phenomenal.