"This is a fact. We just don't have evidence for it."
You do realize that, if that's the best evidence that you are putting forward (a study with 10 participants where the difference was only 20-30%, ie. 2-3 people's perception, where it may not have been blinded), even if it were true, we have no reason to believe that flickering lights have a health impact on people who are not overly sensitive. Until we have a rigorous study on the effects of flickering lights, all we have are highly flawed anecdotes. For example, I saw a 1989 study about lights in a workplace(s) where changing the lights to higher frequency fluorescent bulbs reduced headaches (
Fluorescent lighting, headaches and eyestrain - need a subscription to view the full paper)... but merely changing anything in a workplace, EVEN CHANGING IT BACK TO THE ORIGINAL CONDITIONS, can lead to workers feeling and working better. This is called the Hawthorne Effect where the attention of a concerned observer leads to positive effects (
Hawthorne effect - Wikipedia, the free encyclopedia). In other cases, people in studies unconsciously change their behaviour or feelings based on what they think the experiment is about, which is the Demand Effect (
Demand characteristics - Wikipedia, the free encyclopedia).
So no, it's not that we "do not have very good brains": it's that there isn't any good evidence to suggest that flickering lights have a negative health effect on the majority of people in the population. Even personally, I've worked in an office where we had a defective fluorescent bulb where we could literally see the rapid flickering. It was annoying as hell for the 2 weeks we put up with it but none of us had complained about headaches.