Is "terraforming" the right word for what the aliens began doing on Earth? I may be mistaken, but I thought "terraforming" meant to make a planet "more Earth-like." Seems like a different/new term should be applied in this case. "Xeno-forming"?
You're quite right, but it's a common mistake to use the word generically. There is sort of an in-universe rationalization for it, though; the Votans borrowed the word from English, according to one of the online sources, so they probably didn't understand its etymology and applied it incorrectly, just as so many humans do.