There are two components that define a Linux distribution. The first is the kernel. The other is the core user land that includes the coreutils and libc. This part is made of GNU coreutils and glibc or compatible alternatives like busybox and musl. Every Linux distro has this. The other user land software stack are also similar across distributions, like X/Wayland, QT/GTK, dbus, XDG, etc.

In Android, everything in the user land is different. It doesn’t have the same coreutils or libc unless you install it. ls and find are so common across *nixes that Android coreutils may be reimplementing it. Then you have APKs, surfaceflinger, etc that are not part of regular Linux distros.

An easy test for this is to see if a Linux program compiled for your platform runs on your OS. Linux programs easily run on alternative distros. But Linux programs won’t run on Android or vice-versa, unless you install a compatibility layer.

Maybe I exaggerated, but what I meant is that Android lacks many ubiquitous components of Linux distros. For more information you can read https://arstechnica.com/gadgets/2009/02/an-introduction-to-google-android-for-developers/.