Plus, it's hard to winnow out which particular commit broke something; you're stuck with a ginormous monolithic patch. And sadly, not the 2001 type.
It's not quite as bad as tarballs (in the kernel, you'd have to first generate the patch) but it's not far off.
And then the other thing of there are people interested in using the tech in other places (the supercomputing thing in the article above) but are stopped by Google's foot-dragging. This is hardly ideal.
It may be the minimum required, but do you want to just have the minimum pieces of flair?