I'd have to check, but I wonder what pitch the song is in? Could have it just been sped up ever so slightly in mastering, or even just between tape playback from mixing to mastering?

I have to wonder if this is like Dark Side of the Moon/Wizard of Oz - viewers can imply all sorts of intent that is very unlikely to have been there originally. A small mistake or tweak in any layer of processing could have easily done this.