So much to unpack here.

GNU is not a Linux variant. It is a set of programs and shared libraries.

ISO 9660 has nothing to do with compression. Just calling it ISO isn’t a good idea for an intro class like that because it is a set of MANY standards. They should have put a little side blurb and called it ISO 9660 in the table.

tar is an archive tool. It has no compression.

Why no mention of compression algorithms algorithms vs archive tools?

Why not have different compression algorithms and their tradeoffs?

GNU is not a set of programs or libraries, it’s an operating system.

GNU packages is what you are referring to. But GNU itself is the name of the OS.

It was intended to be an OS and is if you use the Hurd kernel. In practice, Hurd isn’t really used, so it is just a bunch of programs and libraries. I guess it can go either way.