Strobe / photic stimulation

I am new to this community and I tried sending to help - but this may be the forum to see if anyone can explain this for me. During EEG tests, I understand that the strobe / photic stimulation is used as well hyperventilation - to actually try to INDUCE a seizure - and register its results / areas of the brain, etc. on the EEG. It is done with they eyes close but fairly close to the face - but why does the light flashing interval keep increasing to very fast levels? Is this because the brain did not actually "seize" yet - and the higher up the more likely to "seize"? And is it true that every brain - even a "normal" person - will have an outer limit or harmonic interval from the strobe light and actually record some kind of seizure-like disturbance? So is the purpose of the strobe increasing the speed of flashes to find the outer limits of a particular brain? If someone NEVER seizes - though they had suspected epilepsy - is that a particularly strong brain - or perhaps it is another abnormality? I'm not sure at this point what is normal or is not. I'm kind of lost on why these tests need to TRY to record seizures or weaknesses. Is this a little like a stress test for heart patients? But it seems a little dangerous or even harmful, certainly painful? Anyone can help me with understanding this - I'd very much appreciate it. Thank you in advance.