For any charger to properly measure accurate Battery Voltage, they need to have Volt meter measuring wires right at the battery posts, it cannot be real accurate if the Vdrops on the battery power wires are not factor in. So far I have not seen any SCC or charger with the measuring wires setup.
You need calibrated meter as the master to be able to find out which meter is right or wrong to see if they are within its published spec.