Ubuntu: "We have no plans to fork GNOME" (derStandard.at)

You didn't ask for a good proof, you asked for "ANY proof". And I don't have the time to do a complete web survey for you (I do note that there is only one side of the debate providing actual facts backed by external links here, and it's not yours).

I do suspect that a literature major would have a field day collating all the public Shuttleworth interviews, blogs and articles, and counting all the occurrences of:
1. some FLOSS players need to do foo or bar (when those players are totally outside Canonical's control, but the words used imply to non-technical reporters Canonical either has this kind of control or is owed it)
2. Canonical wants others to do foo like it is going to now, followed later by “see how influent we are, we asked for foo and others *are* doing foo now” (when they were already doing foo long before Canonical realised it was a good idea)
3. Canonical is going to invest heavily in foo, and the future will be wonderful (when the heavy investment never materialises except in press articles)

Taken alone each of those is pretty innocent, repeated again and again they create a perception in the press which has little to do with reality. This is what I call a deliberate marketing push.

But feel free to point out examples where Canonical has actually given the press an accurate assessment of its capabilities.