Good grief! What's all this "inches nonsense" when talking about film formats? As long as we are in agreement about using metric for our focal lengths, how about doing the same for our frame dimensions? After all, when is the last time a camera manufacturer released a camera and talked about the frame dimension in inches? (Actually I can think of one modern example but will keep quiet about that for now)
Well, there's reality and then there are poor approximations to reality. The poor approximations sometimes lead innocents astray.