I'm guessing that they might have changed the spelling of warg/worg out of an abundance of caution. They had to change a bunch of other names anyway, so why not sprinkle a few extra spelling changes in there, just in case? Apparently they changed enough that they got away with it, even though they pulled stuff like having a light-but-strong, silvery metal "mithral" not to be confused with the light-but-strong, silvery metal "mithril" from LotR.

I wonder what would happen if Greyview were transformed into humanoid form, granting him the ability to obtain treats without assistance...