Well, it's pretty much the only way it would have happened at all because there's no way they could have announced "it's GPL" and had even one of those manufacturers interested. Not even a single one. That's just how it works. Most of those companies have never been involved in anything remotely resembling open source development, so they know nothing about how it works. All they know is "we're giving away our secrets". I think what we'll see is that this is Google's way of warming them up to the platform and then later on going full GPL once the platform's gained some foothold in the market. At that point, we'll ultimately see if Android will succeed and actually convince the phone manufacturers (and providers - they see open source as a security risk) to join them and GPL their work.