Hm, I thought that stereo vinyl records are recorded in a way that vertical groove profile is V=L+R and the horizontal represents H=L-R. It's backward compatible with older mono gramophones that read only L+R and stereo players do H+V=2L and H-V=2R to decode.

Also, while writing this, I realised that it's exactly the same as in the article. Just another way of thinking about it.