He seemed to test it on a bunch of computer monitors, and not a standard 480i consumer television set? The different shadow masks phosphor patterns change how things look
The C= 1084S he uses is a more a (very good) PAL TV than a computer monitor, even if it was sold as a monitor. So "576i" in your terminology. (It was also sometimes sold with a TV tuner, or at least the earlier 1084 (same picture tube AFAIK) was.)
