In a statement to IGN, Square Enix has confirmed that the effect was unintentional, and is removed by a Day 1 patch to the game: “Please ensure that you install the Day1 Patch before playing Balan Wonderworld. We have received reports of a photo-sensitive epilepsy risk from a potential flashing bug if playing the game un-patched. The Day 1 Patch prevents this issue as well as enhances the overall play experience.”
Balan Wonderworld is released today, and anyone downloading a digital version should have the Day 1 patch installed automatically, meaning there should be no risk of seeing the effect. However, those buying a physical version should make sure the game downloads the patch before playing. It’s unclear how the effect made it into the finished version of the game.
Upon its release, Cyberpunk 2077 was also cited as including effects that caused seizures in those with photo-sensitive epilepsy. Those effects were subsequently removed in an update, with a warning added to the game.