I know the feeling all too well. Managing cross-platform frontend development has become an incredibly intricate, so much so that anyone who can bend the browser to their will deserves the "great engineer" stamp.
A valid point. I should've been more clear that this question really only makes sense when talking to a frontend dev. I always try to avoid the "varchar2" style question, a phone interview shouldn't be a trivia contest. For a frontend dev the sticky footer question can tell you more about a persons coding style and thought process. A proficient frontend dev would have an opinion about how sticky footer should be done and be able to identify common pitfalls.