Many GNU projects are maintained directly by the FSF/GNU (the same entity; their own statements acknowledge that they share personnel and have no clear boundary between them). And for many more projects they hold the copyright and provide the funding/hosting/etc. and the named maintainer is either a member or affiliated with the FSF/GNU, which suggests they exercise some control over it (e.g. the published hosting requirements for Savannah say that projects they host "should" follow the GNU hosting standards, which include requiring copyright assignment to the FSF if the FSF holds the copyright).
Well, requiring copyright assignment (not just a CLA) is in their published rules for using Savannah, and something almost all major GNU/FSF projects did in the past. Even if it's now something they merely encourage rather than require (and I'd be interested to see a public confirmation of this) my point stands.
