Yes I agree there is a huge gap between the two. That is exactly why I like to distinguish "GNU/Linux" (even if it is a trimmed down embedded distro that contains less GNU stuff than usually) from "Android". Calling the former "Linux" as opposed to "Android" is weird for me, since the Linux kernel is about the only thing those two have in common. That's like terminologically distinguishing a bird from a cow by calling the bird "animal"._wb_, the distinctions are subjective, we're probably not going to get far arguing over this. Suffice it to say, I've used enough different things commonly called Linux (not necessarily with all of the typical GNU trimmings, I've used embedded with little GNU) and I've used things called Android, and I perceive a huge gap between getting software running on one instead of the other. I have a feeling ssokolow can say something similar. If you don't feel there's enough of a distinction then so be it, there isn't much in the way of hard barriers outside of ABI like ssokolow mentioned.
I don't get how one can simultaneously argue that 1) the kernel is the thing that should determine the name of the OS and all the rest is irrelevant userland stuff, and 2) Android is "something new" and should not be called "Linux".