Thanks, glad you like the game! That sounds like it's a "motion aftereffect" illusion, which if it's moving upwards is actually probably caused by the notes themselves, not the spotlights, since it requires constant movement in one direction (the notes in this case), not something moving up and down like the spotlights. So it would probably still happen if the spotlight were disabled.
That being said I'll still consider it for when I do a revamp of the settings menu. I would do it in the next update (Ch4 maps), but the menu already has a new setting coming that update, and the menu is now completely full, so to add another one I'll need to do a revamp to allow for more options, which will be a bunch more work than just adding a single option, so it'll be it's own update so Ch4 maps aren't delayed any further