That is true of a battery which is not installed in a car like ours. Depending on when you test the battery, like if the trunk is open which turns on the dome light or if the ECUs of the car are still cycling since the car was running, or if the SKS is on and searching for a FOB, these and other things will cause normal and temporary drain. This will cause a lower reading at the battery. These things can be isolated with care such as timing of the testing or disconnecting the battery or running wires from the battery outside of the car and testing after the car has been sitting still for a while. Some confusion is understandable. But the basic points are well made in the recent posts.