It is the author’s opinion, that people, in general, make too much fuss about what they call something they use. After all, they are there to take advantage of other people’s work, it is rarely their job to decide on nomenclature. (Linux kernel and GNU developers are of course an exception from this.) On the other hand, those who create something might want some recognition for it. Richard M. Stallman is generally a lot less recognised for his work on the GNU tools (although he does get recognition for his Free Software Foundation) than Linus Torvalds gets for the Linux kernel… and in turn the whole operating system. Linus is often thought of as the “father” of Linux, while Richard gets the footnote. It is no wonder he insists on naming the system properly, and it certainly sounds a fair request. (Although the size of his beard does not seem to make him fit to be called the “mother” of GNU so that it could be all a big happy family. But let us not go there.)
For the record: The OS these pages are about, is officially called Debian GNU/Linux, honouring Stallman’s role in its development and his wish to be recognised. It does not matter how you call it for yourself (the author usually uses just “Linux”, as it is shorter) but it is probably worthwhile to know about these details.
It is another personal opinion, that one of these figures is usually perceived as “cool”, while the other is often seen as “eccentric”, although you’ll have to figure out which is which, this is no place to be judgemental. This seems to go a long way as for why people recognise/omit some other people, even though they use the fruit of their hard work…