No Arc Flash PPE Required for PLC Panels

I’ve heard that PLC and I/O panels need to be designed to exclude 120V wires or circuits because of arc flash requirements.  On Table 130.7(C)(15)(A)(a) of the 2015 NFPA 70E, it states as long as no exposed energized equipment over 120V exists, no Arc Flash PPE is required to work on control circuits 120V and below.