when you finish changing the oil (without filling the filter) and check the level on the dip stick, it'll read "full".
BUT once you start the car up and let her run for a bit, the oil circulates filling the filter up. Now you turn the engine off letting it sit for a few, then check the dip stick again, you're going to be... let's say 1/2 quart low.
*Also...i'm not sure of the direction of flow for oil in the motor, but for the time it takes the oil to fill the filter up...your motor is running w/out lubrication. This may be a mute point.?
~Ray