it appears that the circuit "in my opinion" act as an instrumentation differential amplifier, with the lower OP-AMP mounted as a buffer in the feedback loop to monitor the load.
for the POTS, if the idea is to simulate a differential input as to measure the CMRR then it would be ideal if this is a dual one where the +VCC and -VEE are connected so that when you increase the voltage on the (+) side it will increase in the (-) by the same amount.. I guess..
Best regards.