New patent describes a super compact OVF (for small DSLR or mirrorless?)

The latest patent spotted by Egami (translation here) describes a Canon developed Optical Viewfinder with 100% field of view. The special thing about that patent is that the viewfinder is a lot smaller than current finders. It sounds like a perfect solution for a new super small Canon DSLR or a future Mirrorless camera with Optical or Hybrid viewfinder. Otherwise…why do it that small?