I can't tell what your interviewer knew or intended, but the point of the question it seems to me is the "one non-Braille bump on the '5'" solution is actually better and simpler than using actual Braille. So answering Braille actually does seem wrong to me, and insisting it's not wrong seems like missing the point. You had generalized Braille to mean any bumps, so maybe your interviewer knew what Braille was, and that this was not Braille, and thought the point of the question was specifically that it was not Braille.