[Mick]

I'd guess it's just a timing issue.

To be honest I wish the original Playstation had done this because when that (and most other consoles of that period) was used with RGB scart on a CRT television the picture always shifted to the left, creating a black bar along the right and losing some pixels/overscan along the left, very few games had an option to shift the picture so it was either have wonky picture or suffer with poor RF quality.