GNU is not either the operation system as without Hurd, Linux or some other kernel you can not use the GNU tools. GNU/Linux is a collection of software which forms the operation system though this collection can contain even more software and with different collection it becomes different operation system which is why Android is Android and Ubuntu is Ubuntu, etc. But Linux will always be the key component of operation systems using Linux as kernel and we Linux fan boys will always be happy when Linux is used as a Kernel and will follow metrics about operation systems using it.