It's my understanding that the "conduct policy" signs are more of a CYA for the mall, than anything else. If an incident occurs, the mall can point to the "posted conduct policy" if somebody starts talking lawsuit. If somebody starts asking why the mall hasn't prohibited "those evil guns", the management can point to the conduct policy signs, and that would calm most who might have a panic attack caused by worrying that somebody might have a gun in the mall.
Such signs (the ones that I have seen, at least) are not legally binding on permit holders, since they are not posted so that they can be easily seen before entering the building and don't have either the required wording, or the circle and slash over a drawing of a gun.
ETA: They are supposed to post all entrances that are normally used, for the posting to be legal.