More mystery: The 35mm IB Technicolor print has the same runtime as our 16mm print.

Maybe WB constructed the 81min cut and George, et al. had a hissy-fit and left everything else up to WB in disgust, but WB decided to release the 85/86min cut in the US to earn money from the growing "Art House"/Indie scene and release their 81min cut elsewhere (e.g., Italy).

My knowledge of this film isn't great. What evidence do we have of the 81min cut being released in the US besides word-of-mouth?

I wouldn't be surprised by American Zoetrope boycotting the US theatrical premiere only to never find out that it was a slightly modified version being shown rather than a butchered one.