This doesn’t account for blinking.
If your friend blinks, they won’t see the light, and thus would be unable to verify whether the method works or not.
But how does he know when to open his eyes? He can’t keep them open forever. Say you flash the light once, and that’s his signal to keep his eyes open. Okay, but how long do you wait before starting the experiment? If you do it immediately, he may not have enough time to react. If you wait too long, his eyes will dry out and he’ll blink.
This is just not going to work. There are too many dependent variables.
As a software engineer who started programming when he was 11, I get what you mean about “ladder climbers” feeling alien (my elitist term for them is “9-to-5ers” or “pedestrians”).
However, I think this question is dumb at least so far as it won’t work to weed out the people you think it will. I don’t read fiction often, and the only scifi books I remember reading are Dune and Prey, but that’s very out of character for me. It’s pretty much luck that I read those, and more a factor of me just being an old fart (I’m almost 30, and that’s a lot of time to stumble upon at least one scifi book). Ask me this question a few years earlier and I’d draw a blank.
Both were good books, but nothing that would consider a “favorite”. Dune is memorable to me just because it very clearly was based on Lawrence of Arabia, which I found neat. As for Prey, I only vaguely remember something about killer nanomachines, and that it was a fun read.
But if you’re specifically looking to hire someone you can talk scifi novels with, then it’s a very good question (as long as you’re mature enough to hire someone who says their favorite book is one that you hate).