Alpine's userland is replacing the dependencies of GNU packages, the same way Stallman was replacing the dependencies of Unix packages. Simple as that. Sure, you can do the same with Android. And perhaps one can make a complete Unix-like Bionic+Linux system with Wayland and all that. But I haven't seen one, all of this usually runs on top of Android packages. It runs natively. Very well, that's fair. But these utilities are not what Android depends on. If I ported the coreutils to BSD, would that make it GNU? No, not really. I still won't be able to run software made for GNU+Linux.