Well, thing is the blu-ray player in this, and the base PS4 could both support 4K UHD discs, just need a firmware update, laser is compliant.
Thing is, Sony is selling their new stand-alone 4K UHD player for 200+. No reason for them to compete with themselves.
I can understand where they are coming from. Also you have a good point, I doubt a lot of consumers know or care about 4K UHD. when blu-ray was first out, many were surprised that a lot of movies on it were just 720p, not 1080p like everyone assumed.