Erm...
In one of Oli's answers, he mentions :
[Questions] how it's installed (and how it boots) are not Ubuntu proper and are off-topic.
That's firmly within the context of Crouton, which is a hacked-together way to shim Ubuntu onto a Chromebook.
Grub in the context of Ubuntu is on topic. It's an officially supported application that couldn't be any more a part of Ubuntu if it wanted to be. Why would we ever consider that off-topic?