I don't think anyone is debating whether it works or not. I think they are saying it's easier* to design lenses for larger mounts. *What "easier" exactly means is a bit dubious tbh, could mean more compact lens or lenses with less corrections hence glass elements i.e. permitting simpler design lenses. Then again look at FE55 I can't really see canikon making a lens that's sharper and/or smaller. It's all very dubious, we haven't had any credible optic engineers comment on it to fully understand the issue.