I smell a rat. This makes no sense.
15 U.S.C. § 1125(a) creates a civil cause of action for claims of false designation of origin and false advertising. This provides federal protection for unregistered marks.
Do you expect that MS and Google are going to fight a civil suit to protect your trademark? Or do you have to sign over the rights to your trademark first, which means you no longer control the trademark. You no longer control your project.
Who benefits? Well if MS and Google get people to "sign over" their trademarks then they can freely define what the trademark means. This would feed into the MS embrace-extend-extinguish technique. The end result is that they effectively "own" open source projects. Imagine if MS or Google owned the Linux trademark and were able to define what was "officially Linux".
This sounds like a "collect the trademarks" competition.
Corporate pokemon.