How is v0 impossible for cia though?
Correct me if I'm wrong, but doesn't v0 just mean it's a cartridge dump? How does that make v0 incompatible with a .cia file?
Not incompatible, impossible, as in, for a legally obtained game. Only illegally obtained digital copies can ever be v0. If Nintendo now have some way to see whether someone is playing digital or cart and also see the version number, someone playing digital v0 is instantly known to be a pirate because they do not legally exist.