the distinction is between "Linux" and "GNU/Linux".

technically, "Linux" is just the kernel, that is correct, but usually when people talk about "Linux" they talk about distributions such as Ubuntu, Fedora or Debian, and that includes the GNU part of things as well.

saying something runs "Linux" implies that you can use the same software tools to write and compile software for it, giving you access to a huge amount of open code. but it just isn't true. Google does this intentionally, fraudulent advertising IMO.

you need completely different tools and libraries to write for a completely different environment. you don't write "Linux" programs... you're as far away from the kernel as you can get.

so yes, in my eyes, Android definitely isn't Linux. With Maemo you get nearly all of the standard Linux parts there are.