Of course that's true - with the rather crutial difference that we do not insist on calling it "Linux"! :-)
I never ever corrected anyone to say "Linux/Ubuntu" instead of just "Ubuntu", or to say "Linux/Android" instead of just "Android".
This whole GNU/Linux naming crusade is just that: a crusade, trying to force things on others. You need to stop 'correcting' people when they say Android, Ubuntu or Linux, that they should say "GNU/".