There are the layer combinations for work and the layer combinations for output. In the past, the output LCs have had all their layers locked. The only reason for this was make clear to the user that they're not in a working combination. Not a critical point but there it is.
Now there's a stronger reason to have the layers unlocked in output LCs. In AC10, you can right-click on a drawing and choose 'Open source View' to, right, open the source view. (In AC/PM9, this command existed but it never worked as far as I could tell.)If you are viewing a drawing and see something that needs fixing, you can open the view and get right to it. So the layer locking should get out of the way.
In the architectural LCs, all the visible layers are unlocked. In the specialized plans (electrical, e.g.), only the special layers are unlocked.