Motorola was bought from beginning to use as a leverage tool against patent trolls like Apple and MS. What did you expect? VPx is intended to be open from beginning by Google.
You can never expect that, because you have no guarantee against unexpected patent trolling. Apple and MS are just looking for excuse to sabotage open codecs. But real threats come from themselves and unknown patent trolls.
The FTC would seem to disagree with you as they believe patent commitments to standards are not changeable after the standard is adopted. Once again Apple and MS don't care if its open, they care about stability.
Your post, makes my point. Why would Apple and MS expect Google not to do it again?