Yes, I'm sure your analysis is correct! For anyone interested in the technical details, here is the reason (as I know that you already know ).
Thank you for your precise explanation. At first, I was about to try to explain the detail but I've quickly changed my mind remembering, “Seeing is believing.”. I also thought that my limited English would not be comfortable for you natives to read and I just uploaded the corrected photos with the minimum calculations.
I always appreciate your excellent support for me with those Hayley's videos in Japan and things like these. My HDD video recorder records NTSC's chroma burst signal some as a green vertical line at the right edge of the screen. But once you edit the videos, everything becomes perfect. I always think that you really are a good video guy as well as a good manager.