You have good ears, just as you did back in 2015.

https://soulfuldetroit.com/showthrea...rack-3-version

My ears tell me that the single A and B sides of "This Old Heart Of Mine" do actually consist of those unique stereo mixes folded into mono.

I suspect that this single is unique in that respect as far as Classic Motown goes, although I'd love to be proven wrong, if only to hear other examples.