They can contribute without having any special status. Rust already has a robust RFC process and good technical leadership. My worry is that these things weaken and rust very gradually becomes your typical corporate software product where more and more independent features are just bolted on without care to any larger vision. That won’t happen if FB, etc keep contributing as ordinary contributors. But it could happen if they’re elevated to a position of leadership.
Note that the Foundation doesn't have any impact on the RFC process or the project's structure or governance, so while that worry may exist, this announcement isn't a path towards doing that.
