I see. Thank you for doing that investigation work. Roughly a year ago another user has essentially the same issue also when using two identical monitors. We found a way to disambiguate using the location reported by Windows in the registry in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\DISPLAY\[YOUR DISPLAY ID]. I ended up taking the location reported, hashing it (converting it to that number you see), then using that to find the display when opening MiniMeters. It seems in your case it's reporting the same ID, which was presumed to not happen.
Would you be able to check that section of your registry to see if the path inside your display's ID is unique to each? Additionally, could you please check to see if the EDID in "Device Parameters" is also unique to each individual display?
