That's a very good point, even besides the contributions there are some Apache licensed components in AOSP that Google have brought in themselves rather than had donated.

I guess in my hypothetical scenario, they could relicense them as GPL but then they'd have redistribution requirements via GPL virality - at least for those bits.

Or they'd need to restructure their parts of the project around them to avoid the viral aspect, like they have for the Linux kernel.

I guess my point is more that not every part of every Free Software project is always released to the public under that license. "Android 3.0 is not Free Software yet, but will be" is not that different to other common OSS project scenarios.

But if they were GPL only, it's much more likely they'd ask for assigned copyright, in order to achieve the same thing.

To be completely 110% "open" you'd GPL (or even AGPL) and not ask for assignment, which would level the playing field for everyone. But it's not common for business sponsored projects, or required to be Free Software. And again, even RMS accepts that there are strategic reasons to use non-copyleft licences for e.g. audio and video codecs as widespread adoption of proprietary alternatives would harm Free Software.