The foundation supports a bunch of other open source projects, after all there is a lot more to devices that run the Linux kernel then just the kernel.
Also, I found it a but funny that the foundation created the PDF using Adobe InDesign 19.4 (Windows), according to the metadata in file posted on their website. (original | archive of the PDF)
Some older consoles have very negligible size libraries in modern day terms, and who knows what sources of ROMs will be taken down by lawsuits in the next few decades. I feel like there is some sense in making a complete archive of a systems game library, but for my personal use I usually just download / dump / rip what I need specifically.