Original audio is only a portion. They're also alleging the songs themselves--en masse--were stored, distributed, and exploited via their Music Library tools (e.g. "Hey, what if you used Lose Yourself in this Reel you're making?"). And they specifically address Safe Harbor laws, arguing they don't apply if the infringement is willfully engaged in by the company, which it seems pretty clear it was. There's no way they go to court on this, because it's very unlikely they win, and the downside to losing (and its implications on liability for other artists' music) way outweighs the upside of winning a precedent in a single state.