Earlier quoted context omitted.
Android uses the Linux kernel, with a Java/Kotlin userspace.
As RMS is quick to point out "linux" is only -ever- the kernel. So yes, android is 100% Linux. It is not Gnu/Linux though. Which is what the desktop folk are celebrating. This is one case where the distinction actually is important.
Or how despite having an endless choice of games, and applications, almost none of them are available in GNU/Linux.