The only thing they couldn't do with C418's music, was to publish "Minecraft: the official soundtrack" and take all the royalties themselves. Nor could they claim YouTube videos for having Minecraft's original music in it (they did it several times "accidentally" when the movie came out, and stole a couple of million from YouTube makers).

So no, I don't buy the "they'd have to go through lawyers" excuse. They could still have had blanket licenses for using the music in all sorts of ways, they just wouldn't own it.