In the CSS property index, the background and border properties all reference CSS 2, not CSS Backgrounds and Borders Module Level 3, which I'd treat as the stable version (Candidate Rec since 2014, and I think just waiting on a few tests for progressing to Rec).
One particular consequence: background-clip isn't listed in the index at all.
CSS Backgrounds & Borders Level 4 is linked from the Index in a couple places, for the properties with major changes, but that is still a "diff" spec, relative to Level 3. So it can't be the primary reference.
I haven't checked, but I wouldn't be surprised if the indexing method is similarly confused by diff-style drafts of other specs.