I think that a lot of these alternate / slightly different takes sometimes come about by pure accident. The UK label requests the tapes for a particular track and someone in the US record label tape store just pulls out a tape with the song title on, probably not aware that it's a different take.
Some of these differences took years to become 'known' by the collectors over here (or anywhere else). Pre internet, things like this were mostly word of mouth and not always common knowledge.
Another to add to this is the UK London release of Chubby Checker's "You just don't know"
I've never heard it mentioned that that release is sightly different from the Cameo Parkway release.
The drumming on the London release is way more up front in the mix, almost dominating the recording.
Whether it's a mastering thing or a different take, I'm not sure, but it's definitely different.