Well, this is a slap in the face. ChromeOS has had a long-standing tradition of requiring device kernels to be in their tree. Giving them a better shot at long-term/community/Linux support.
It's hard to not cynically read this as "we're making it easier for our partners to ship devices with vendor kernels".
I'm pretty shocked. I would've bet good money at this having gone the opposite direction, with ARC already on ChromeOS, etc.