Testing out an Allen Bradley 5094-OB16 without a load wired to the card gives 24V when on and 14V when the output is off. This remains true as long as the SA power is on and the module is in the slot regardless of if there is backplane power.
It was confirmed with Rockwell that this is “normal” with no load. We should see a lower voltage (5V max) once the end device is connected and the load is above 1mA.