It's not about whether you can "see 240Hz". CRT phosphors have sustain, while OLED does not. The fully-on, fully-off cycle, if infrequent enough, causes some sort of visual stimulation that some brains absolutely do not like. You don't have to see it to feel it.
Sometimes I can tell flickery fixtures because they just "feel more staticky". I don't get visual eyestrain or nausea though.
What exactly do you mean by "not the same thing"? Using a device means moving your eyes, among other things. I don't exactly stare at a specific point on the screen for the 63 Hz visual persistence to take effect and I'm pretty sure 95% of the other individuals of this world don't do that either
Other than some old monochrome CRTs, all CRT phosphors decay too fast to prevent flicker. You get some softening of the trailing edges of the phantom array images, but they're not actually blurred together like on a sample-and-hold display. And even the fastest CRTs have fairly low refresh rates, making it more obvious.
Sometimes I can tell flickery fixtures because they just "feel more staticky". I don't get visual eyestrain or nausea though.
It's not magic. :) You DO see it. 500 Hz for the median observer; above 800 Hz for some individuals. https://doi.org/10.1038/srep07861
There is still some ability to percieve strobing at a steady state though, even if the amplitude is reduced by visual persistence.
Other than some old monochrome CRTs, all CRT phosphors decay too fast to prevent flicker. You get some softening of the trailing edges of the phantom array images, but they're not actually blurred together like on a sample-and-hold display. And even the fastest CRTs have fairly low refresh rates, making it more obvious.
what about old-timey film projection? thats ten times slower and fully on/off?