So it looks like the collection has already leaked, and the big news is all 3 games are emulated. Nintendo's own internal studio, NERD, who created the emulators that the NES and SNES mini used, which are the same the Switch online uses, has created a new N64, Gamecube and Wii emulator.
This is pretty big news since it means Nintendo has a working emulator for all 3 systems on Switch. So the reason Galaxy 2 isn't in the collection is more then likely a Wii Online is someday getting added to the system, or they're going to start individually selling Wii games again like the old Virtual Console.
So yeah, it was corporate greed the whole time.