List of theories will be in another thread.
Notice: sensitivity to one kind of flicker doesn't make you automatically sensitive to other flickers.
Flickers are very different, they have different parameters and different levels of visibility.
Random examples:
Post where a person is sensitive to dithering that can be disabled by ditherig, but not sensitive to 200 Hz PWM (Russian)
Post where a person is sensitive to different sources of signal (OS, GPU), but not sensitive to PWM, and all his safe screens have easily detectable PWM (Russian)
This is also true for every other problem mentioned here: sensitivity to one does not automatically mean sensitivity to others.