It’s not just the number of photosites, or even the bit depth - Netflix approved cameras need timecode support, among other features that distinguish a “production ready” camera from a consumer one.
A lot of cinematographers don’t really like the extreme resolving power inherent to 4K+ sensors, and optics that diffuse that sharpness (for instance, a lot of anamorphics) are VERY much in vogue as a result.
