Req 1 assumes static browser model

[marcoscaceres]

The doc reads:

A User Agent must support technology commonly available on desktop browsers, so that Web sites and applications designed for desktop are still usable on mobile.

This requirement is really about keeping mobile browsers up to date with desktop ones - which are evergreen. Browser rot on mobile platforms is a significant challenge that developers face, particularly on Android (e.g., 2.2. is still being sold!!! 👊).