In common parlance, yes -- because there is no practical distinction. But in cases where something is just using the Linux kernel without GNU and other common userpand components (and there is a practical distinction) then it's definitionally untrue to say that it's "not Linux" if you really meant to say "it's not GNU/Linux".

Alpine Linux is not using GNU. I'm sure there are others. No definition you can ever come up with will have no exceptions in widespread use. Live with it.