This was a popular thing to do in ye olde commodore 64 days, because you could cycle the background color easily in basic, and nobody thought yet that a video game could trigger epilepsy
(honestly, I'm a bit skeptical about this theory even today, but will defer to the typical opinion on this matter, not being an epilepsy expert)
That’s real. I once wrote a quick & dirty bookmarklet to disable all GIF animation on a page because even fairly unremarkable-to-most-of-us GIFs are uncomfortable for an epileptic friend. It is still on https://alanhogan.com/bookmarklets
I wonder if it's better for people with epilepsy to have a simple and more robust solution by getting a monitor that has low refresh rate or limited colors than to try to police all the internet and applications from ever showing flashing colors.
They may and if I had epilepsy then I'd look to do the same, but that won't absolve us of the need to take care so that people without special equipment don't need to worry.