Actually that is a common misconception by people who have read political blogs from the 90’s.
The OS that you are calling GNU/Linux is usually less than 2% GNU these days as the GNU Project is only responsible for about a hundred packages. Most Linux distros have between 3,000 and 80,000 packages depending on the distribution.
In fact, if we are talking about software licenses, calling it MIT/Linux would be more appropriate. If we are talking about attribution, Red Hat contributes more code than anybody so perhaps Red Hat/Linux is more up-to-date. That may cause confusion with Red Hat Enterprise Linux though so perhaps IBM/Linux is the best term to use as IBM owns Red Hat these days and is therefore the top contributor to most Linux distros.
Of course, most people just call it Linux because everything above is ridiculous ( including GNU / Linux ).
All that said, teaching people about the FSF, copyleft, and Free Software more generally is super important. The GNU Project itself is more of a historical artifact at this point ( in my view ) but there is no denying its extreme historical importance. It would be great if people knew more about it. Much like BSD.
Teaching people to say GNU / Linux is not only not important but is downright political and factually incorrect. Not a fan.
This is exactly what people mean when they say GNU/Linux. They are trying to say that it is “the GNU Operating Syatem” with the Linux kernel.
This nonesense though. Please ignore them.
Linux Mint is an operating system. It uses the Linux kernel. The fact that it includes a handful of GNU packages in no way justifies co-opting the branding. Linux Mint includes A LOT of software from many sources. Are you going to try to list them all in the name?