Blu-ray.com lists it as LPCM 2.0.
Yes, exactly. My point is that it doesn't make any sense unless the original alleged 4-track release only used two channels.
I expect stuff like this from the majors ("Jesus Christ Superstar" had 4-track mag prints...the first, non-anamorphic DVD was DD 4.0 but every release since including the Blu-ray is 2.0), but for Criterion to do this without explanation is weird.