You're correct.

Well now that I realize you have a rotary pump, adjust the pump discharge pressure up to, say, 11.5 bar with a blind filter in place. There should be a drip . . . drip . . . drip from the OPV relief back to either the drip tray or the reservoir. Adjust the OPV such that this is the case and then readjust the pump to your desired brew pressure (9.0 bar?)

There should be NO FLOW from the OPV relief port during normal brewing as it functions as a thermal expansion valve in your case.