Exposed Drywall Paper

Originally Posted by DaneMcCloud

Why not throw some mud on there?

Just a question from a non-professional, not a disagreement.

For the same reason you can't wet-sand it. Mud is going to moisten the torn paper and make it a mess. It won't sit down and dry properly without being sealed first.

In some cases, it will work - like if you're putting a heavy coat of mud on top that mud will harden and probably be fine but if you're just skimming, the paper will bubble, separate from the gypsum, and never sit flat for a nice finish.