A hundred times this.
Far from a PWM issue, most likely the cheap displays that illustrate this issue have insufficient power smoothing, and the culprit is likely the 100 or 120 Hz fluctuation from rectified AC, or (yes, some are really this bad), 50 or 60 Hz from clipped AC.
The duty cycle of a CRT phosphor group is in the order of 1/1,000,000 for an SDTV resolution - the point intensity of the energised area is unimaginably bright; look for high-speed footage of a TV to get some idea of it; or if you have a digital camera of some worth, take a pic at 1/2500 and see how many lines are still saturating the CCD.