The Robot Rules specification clearly states that ALL components must be rated at 125 psi or higher. You have to provide documentation to the inspection station for non-KOP items to support the inspection process.
Many conventional directional valves, such as the KOP Festo and other manufacturers valves have maximum ratings a little below the FIRST specification of 125 psi. Therefore the valve you are buying to operate your robot will not pass inspection as the rule was originally written.
Plus there is the possibility of clever mechanisms creating an overpressure situation on the working pressure side of the system.
Therefore FIRST allow the use of a pressure relief valve on the working pressure side of the system that will protect both the directional valves and system designs that could create an overpressure situation. You could install a relief valve to release at 75 psi which would protect 100 psi rated valves and allow a 60 psi system to operate normally.
An example of this relief valve is the E292
here