That's great, I don't expect an academic explanation but just having heard of it is pretty good. That question by itself is not a deal breaker. An 'engineer' should at least know about things like data structures or just anything beyond Rails. Most interesting problems require more than knowing how to create CRUD apps.

Yeah, I agree. This is one of the pitfalls of working in a fairly unstructured and nascent industry. Everyone seemingly has their own collection of miscellany and trivia that encapsulates what a Good Engineer (tm) ought to know.