I've forgotten more than I know, but I know where to find it.
For many problems, someone tackling it might not even understand that there is a problem, and might have no clue where to start searching for answers.
I've seen many developers who burn a crazy amount of hours by going down the wrong path, and then try to StackOverflow or Google their way out of the mess they initiated. It takes experience (either gained or learned) to avoid such traps.
Then again, it really depends on the job. The interview question suggests this was not for a CRUD job, though :)
Another question was about some low level assembly performance instruction trick. Afterwards I did the same thing and tried to figure out which text book I would have had to read to know the answer. I only found one Computer Architecture book that mentioned the instruction and that wasn't the book I read in university.
For my first 3D game dev job I just turned up with a floppy which had my 3D engine on it and got them to stick it in a PC. That was all that it needed to get hired. That and be incredibly naive about salary negotiations :D
I also turned down a possible position at Argonaut at Star Fox time. I got that one by arguing repeatedly with Jez San on Usenet lol
A close sibling of this mentality lives in academia as well, manifested as that professor who bases 50%+ of one's grade on the final. Also, pass/fail filtering exams (and the cultures that endorse them) generally, such as the MCAT.
This was less true for my Master's and is generally less true for non STEM.
I kind of liked it tbh