Urr, I don’t think that’s it. I’m not sure stereo sound for vinyls has ever worked so that something like this would be necessary, and it wouldn’t really make sense – why would they have to put vocals on one channel and instruments on the other?

A stereo vinyl player just has the needle moving up and down in addition to left and right, so that the left-right axis is the sum of the waveforms of both channels and the up-down axis is the difference – which means that a regular mono player can play stereo vinyls