aua
Great find! Seems likely. Apple has been using dithering since at least 2007 (confirmed by a lawsuit when they were using 6-bit+FRC to approximate millions of colors) so this is entirely possible.
If we are to extrapolate the anecdotes from iPhone SE users, it seems that less capable screens will be more likely to dither, and dither more often, on later operating systems that were designed with wider color gamuts in mind.
I’m trying to think back to using this iPhone 5 which I believe I used until 2018 when I got the X, and I do recall eye fatigue when texting for long periods of time. I was in my early twenties and chalked it up to screen time. But seeing this now, it’s clear dithering was making it difficult.
I also want to clarify my first post. For the second video that is dithering, I used a gray photo I had downloaded back in 2016 (it was the inside booklet of David Bowie’s album “Blackstar”)in the photos app so it wasn’t a recent image. So this is accurate to what it was doing a decade ago.
I don’t believe the screen is damaged or flickering otherwise because the backlight is steady on slow motion without microscope and the first video is dithering only on the pixels that have gray text in Safari. If I can detect this on 240 fps slow motion it must be dithering quite badly.