All true. But Wii does play Gamecube disks, had a lot of the same internal architecture, and was called "two GameCube taped together" quite frequently; Switch does not play Wii U games, GBA does not play SNES cartridges.
None of them are revisions, obviously. They're all clearly new systems that just happen to share some games and technology with prior systems.
While it is a new system with a new OS and interface, from a hardware perspective, the Wii can be justified as a revision of the Gamecube. That is why people were saying it. The prototype Wii was literally a GameCube and a Wii remote.
This is why I said, if anyone wishes to consider the Wii as a revision of the Gamecube, that would be IMO objectively the best revision of Nintendo hardware in company history. Otherwise, GBA SP. My personal favourite is the DS Lite, as I skipped the SP and actually played most of my GBA games on DS and DS Lite.