How do you know that? Crawling has a lot of fills in it, but it's nearly impossible to pick them out with the rest of the song. You can only hear it when you listen to the multitrack. Who knows what the other songs hold. There's a fill on Papercut that doesn't follow the guitars at all, for one.
Plus, I'm fairly certain Forgotten has little to no variation on the bass from the guitar root notes. The verse bassline is just the chorus bassline with a slightly different rhythm (I believe, but I can't really hear what the rhythm is for the chorus, it may very well be the same).