A TCM showing of this film just started, and unfortunately I can't stay up to watch the whole thing (it's now after 3 am EST), but there's one thing I noticed:
The original release date was supposedly January 1968, according to dvdbeaver.com, but shortly after the opening credits a couple of minutes of "Shhh/Peaceful" by Miles Davis, from his In A Silent Way LP, can be heard in the background. In A Silent Way was not released until 1969. So some music must have been added after the initial release.
OK, according to a Criterion webpage ("Symbiopsychotaxiplasm: Still No Answers"), the film was actually shot in the spring of '68 and first shown in 1971. So that answers that question. As Emily Litella would say, "Nev-ver mind!"
Presumably the director got clearance to use Miles' music. (Then again, given the nature of this production, who knows?)