There's kind of a crossword language, especially if you do NYT where there are regular callbacks. Some of them are pretty weak, actually, but they're shibboleths of sort to regular solvers. We complain about weak fill, but they're like clues in themselves.
As someone that does lots of crosswords, this doesn’t seem at all out of the ordinary. I guess the difference is that in a regular crossword, these cultural unknowns can be worked around if you can get the crosswords, but that’s no guarantee either.