That is arguable. The opinion that an OS needs userland apps come from those with a Unix background, you need those apps to be a Unix, you need them to be POSIX compliant.
The kernel is necessary but not sufficient, and the S in OS is for system, the kernel is part of the system, not a system entire
How so you differentiate with non-Linux GNU systems?
The kernel is the OS
That is arguable. The opinion that an OS needs userland apps come from those with a Unix background, you need those apps to be a Unix, you need them to be POSIX compliant.
The kernel is necessary but not sufficient, and the S in OS is for system, the kernel is part of the system, not a system entire