Agreeing with all that, the distinction isn't made in general speech or writing.

MVS, CMS, VMS, OpenVMS, UNIX, Ultrix, Solaris, AIX, HPUX, DOS, CPM, BSD, MacOS, Windows, BeOS, iOS, Android.

GNU/Linux.

There are times you might specify the user environment. MVS TSO/ISPF, say. Or hardware: VAX/VMS, SolarisX86. But not elsewhere the libraries.

I get RMS's rationale. I largely support and practice it. But it runs against convention and practice through the rest of the industry, for decades.

And mentioning Debian, it's also available without Linux.

Though I agree also really packages & policy.