Can you elaborate on this? I really don't understand why you say this. In a GNU/Linux distro Linux provides the kernel, and GNU the userland tools. How can GNU/Linux be a subset of Linux? Your next sentence makes it clear you don't mean superset, so I'm lost at understanding what you mean.
(Not GP.) Things that run GNU/Linux are a subset of things that run Linux. For example, the Android phone in my hand and the old ASUS router in my closet are in the latter set, but definitely not in the former. Of course, calling my GNOME desktop GNU/Linux is about as reasonable as calling my Android phone toybox/Linux—both of the mentioned parts are there, sure, but a massive portion of the userland has been overlooked.
Not the GP, but I guess you could say a subset of systems that use the Linux kernel also provide the GNU userspace tools.
Android is an example of one that does not. Although when someone describes an OS as Linux, to me it implies GNU/Linux, so I wouldn't really call Android Linux, even if it uses the kernel.
Can you elaborate on this? I really don't understand why you say this. In a GNU/Linux distro Linux provides the kernel, and GNU the userland tools. How can GNU/Linux be a subset of Linux? Your next sentence makes it clear you don't mean superset, so I'm lost at understanding what you mean.