SC for user agent dependence

I thought a little more about the recent CFC which passed to add a note to the "Full Page" conformance requirement.  I realized that we probably do need a success criterion in addition to this note in order to fully address user needs.

The issue fixed by the added note makes it clear that all versions of the page that have a programmatic dependence need to conform in order for the "full page" to conform.  However, what if those different versions have significantly different content or functionality?  Taking extreme examples:

1.       I display "Sorry, your viewport needs to be at least X by Y to use this app" instead of the working app itself to small screens

2.       I display "You need to be using Internet Explorer to perform this function"

Technically, both of these would pass so long as the different content passes.  My thought is that we need another criterion under the "Robust" principle to address this, perhaps even with its own guideline since it's not always a compatibility issue.  Maybe something like:

"If content is designed to vary based on aspects of the user agent, then each variation includes the same essential content and functionality."
Steve