I just tested in a blank WPILib project either not calling getCANStatus() or calling it periodically every 20ms and every 2ms. The CAN utilization from the DS was stable when not calling it, noisy like your AdvantageKit data when calling it every 20ms, and extremely noisy when calling it every 2ms.
From https://github.com/Mechanical-Advantage/AdvantageKit/issues/71: