The blog post you link explicitly mentions that they have 1080p streams (and since then they have added 4k). That post makes no claims about 720p being sufficie

The blog post you link explicitly mentions that they have 1080p streams (and since then they have added 4k). That post makes no claims about 720p being sufficient for consumers. And if you have the right combination of browser, os, Intel CPU, GPU and monitor to have intact DRM of the required level, Netflix will stream you the 1080p or 4k stream