Yeah, it's somewhat frustrating how some people will screen you for sending a .DOC, and some people will screen you for NOT sending a .DOC. For extra fun, let's ask whether we should wear a suit to the interview: must wear for consideration, or immediate disqualification/no-hire? There's disagreement there as well.

The only safe advice is to ask ahead of time; unfortunately for you, there was no one to ask. Dysfunction is unfortunately common.