Oh, it's there, alright. Professional singer and recording engineer here. My ears are very sensitive to these things, but given how glaring it was to me, I would have thought it would be obvious to most music enthusiasts. It's not necessarily AutoTune; it could be offline pitch correction. It's definitely of that ilk, though, and not something like Pro Tools' Elastic Pitch. It's especially obvious when they transition through pitches very quickly, like at ~1:15 in the video. The human voice does not sound like that, and no group of singers–especially not mostly untrained pop vocalists in their 60s and 70s–harmonizes with that kind of cold, technological precision.