Ah well Paul, you're telling me something I didn't know. The UK Motown office told me, back in the '70s, the original version was cut in LA with Mary and Flo and, then HDH didn't like the backing track and went back to Detroit and cut a new track and recorded some additional backing vocals by the Andantes and layered these on top. Of course, as I have since discovered not everything the UK Motown office told me years ago has turned out to be correct.
Ivor