This isn't entirely accurate. I told my RN Fiance this story and she said "oh 404, that's like... page not found or something isn't it?" She has zero programming experience.
So, basically, somebody who never uses a web browser? 404 and 500 should be familiar just from browsing the web for more than a few weeks.
Modern browsers seem to do quite a bit to insulate users from error status codes in their default configurations.
The people in question do in fact use internet browsers on a daily basis.