I saw this too. It's surprisingly common. I saw the same the same thing with Indianapolis and the NY Giants. It's not always an audible from a pass to a run, it's often a called run where the QB decides where the play is going based on the defense that he sees and communicates this to the team at the line of scrimmage. It's pretty effective, especially if once in a while the audible is to a play action pass that goes over the top of a safety that is cheating up based on the audible.
On another note... We make it way to easy for the defense to double team the guys they want to. TO and Evans are very easy to find. They are ALWAYS on opposite sides of the formation and ALWAYS the wide receivers. If they would line them up in the slot, in the backfield, as a wing-back, on the same side, etc. then it wouldn't be so easy.