This is because of what you define Android as.
Of course, the humorous part is that when all of this first started, Google tried very hard to make sure Android was defined in terms of what the Android Open Source Project was and had, but failed miserably here, so they gave up.
If as you say, Google intended to have 'Android' mean the AOSP at one point, and it has stopped trying for that definition now because it failed to make the distinction to the public, then that only strengthens the point that Google (and you) know that what people think of as 'Android' is not open, and so are knowingly exploiting the ambiguity between 'Android' and the AOSP when you perpetuate that idea.