Well, that can be part of a CommonMark Draft wiki of community editable specifications, which means you could just call the extension CommonMark draft compliant. If you need consistency, then you could implement ‘version system’ for the draft specification wiki (e.g. auto compiles a pdf spec doc every month with a version number).
The issue with making elements CommonMark Compliant instead of CommonMark Draft Compliant is that people will end up expecting it to work in many other places, and probably will just end up getting frustrated. The draft speccing wiki could contain a list under each draft extension, on what websites or software is currently using that particular draft extension.
Hope that sounds more reasonable. If you like it, then maybe I should post speccing level thingg as a new thread and see what’s the general response.
Edit: Posted seperate thread to Multiple levels of CommonMark specification?
In practice:This engine is compliant to 'CommonMark Core' and includes figure extension from 'CommonMark Draft V2.XX'