I don't think the distinction exists the way you're trying to describe. If I should be allowed to install any software I want, surely that includes any .apk I want? Conversely, someone could make the exact claim one step down the chain and argue that you don't get to tell them how their firmware should work and if you want to install your own OS you should just go buy a fab, make your own chips, write your own firmware, and make your own phone. And that's absurd, because users should be allowed to run their own software without being forced to ditch the rest of the stack for no reason.