What are the Labeling Requirements for Electrical Eqpt. > 50 Volts per the NFPA 70E & OSHA 29?

Our company is working on an Arc Flash project for a client with the following SOW requirements for equipment > 50 Volts.
SOW:
"Anything over 50 volts needs to be labeled all the way back to the disconnects."

The following codes are referenced in the SOW: "NFPA 70E, NFPA 70, IEEE 1584 & OSHA 29.

We have been struggling to find sections from a codebook that specifically outlines this requirement.

Per quick research, the Eaton Article below states as follows:
"The owner of electrical equipment is responsible for providing arc flash warning labels which are required on electrical equipment over 50V that could be accessed while energized.
https://www.eaton.com/us/en-us/company/ ... flash.html

Is the requirement for labeling "anything over 50 Volts" referencing Shock Protection Approach Boundaries for equipment that may require examination, adjustment, servicing or maintenance while energized?

Additionally, would the requirement for labeling equipment above 50 Volts & below 208 Volts only have to include Nominal System Voltage & Limited Approach Boundaries(as depicted in Table 130.4(E)); given the NFPA 70E references the IEEE 1584 standard which provides arc flash calculations methods for three-phase AC systems ranging from 208V to 15,000V?