While I cannot give an exhaustive complete answer I think it is safe for me to at least mention that you don't need to be able to perceive it for it to have an impact. You don't perceive even a fraction of what impacts your body, from radiation to chemicals. The molecules still react to lots of other things that are not part of what the eye is supposed to sense. It's not like everything outside light of the human visual spectrum magically has zero impact and you, or the eye's components, are immune.
Example: UV light.
There also seems to be evidence of flickering lights, causing fatigue, even if you cannot see the flickering.
> I’ve never heard of anyone fatiguing from it.
What did you do to find out? If you didn't research it, there would only be random chance for you to find out, accidentally reading a report or being told, plus paying attention and not filtering it out like what we do with the vast majority of what reaches us.
I dunno if the iPhone's face sensor uses that tech, but it hasn't caused any problems that I noticed if so