My bad for not double-checking that, I based my assertion on commentary by others without double-checking things myself 1st...

Fair Qn, IIRC it's something to do with clauses in the licensing or combos (CLA etc) that gives an unfair advantage to Canonical over contributors who aren't part of Canonical.
I know that's very vague, that's why I wasn't specific in the 1st place, I've spent 15min trying to find it but so far nothing, it has been raised many times in threads @Phoronix.
Later I'll try to spend more time finding some of the discussions & link to them, in the meantime look at several of the major stories/discussions in the last few mths & see if you can find it.
I can't recall if all of it was discussed @Phoronix or mostly linked to external sources from there, but I'm pretty sure the entire crux of it has been covered there regardless.