The NES Classic is somehow able to detect rapidly flashing screens in its built-in games and temporally blur them as an anti-seizure measure. Nintendo certainly learned its lesson from the Pokémon incident.
Doing the same with today's visually intense games, like Rez and Tetris Effect, would be more difficult. The potentially harmful visual effects are more subtle than simply rapidly flashing the entire screen background, would require heavy processing to scan for, and if you filtered them you risk compromising the visuals that some people purchased the game for.
Best to just warn them so photosensitive people know what they're getting into.