My guess is that it's leaking in multiple places. Since it's relatively crude by alternating "all black" and "all white" pixels at different "switch rates", it generates recognizable noise in multiple places. That seems to match all the different frequencies you see people reporting to find it. And people finding it regardless of how the signal is getting to the monitor, LVDS, HDMI, VGA, etc.

The "requires a CRT screen" was, I think, referencing the much more fine grained ability to actually recreate what was displayed on a screen. Though that's been replicated for LCDs now also.