As for temporal - many of us CAN see temporal dithering. I don't know for sure that it's what causes the problem, of course, but we can see it on many affected devices. Subtle flickering/flashing (such as on my XBox One) or "movement" (such as on a Macbook, where we can literally see the pixels shifting). But if you eliminated that dithering, it doesn't eliminate the problem in all cases (although it improves it for many), so I suspect there's something deeper, some new video mode.
As an example, on my XBox One... prior to October 2018... the game Destiny (the original) was flawless. I could play for an entire day, sunup to sundown, without issue.
Destiny 2 dropped and IMMEDIATELY my eyes were tired. Same hardware, same OS, same everything. Just a different game. Slime Rancher? No problem. The Division? Cake. Destiny 1? Aces. Destiny 2? OUCH.
Clearly there was a new video mode being engaged, or some dithering. Or anti-aliasing. Or SOMETHING. Not sure what. But then a year later? The OS updated and now ALL games hurt. So whatever new mode it is became global on the system.
That's the sort of thing we're running into here. 🙁