Fun with solar and Renogy MPPT 30 Li (kind of)

Battery voltage on the controller display is 12.9, and voltmeter connected directly to battery terminals reads 12.91.
There was no difference when I dropped the load terminals on the controller and connected the load directly to the battery. Same "demand effect", same false 90% SOC at 12.9V.

Which leads me to believe that it's controller that is at fault, - its hardware or firmware or both.