Function of bypass filter: Oil pressure from engine pushes oil to filter canister. Oil passes through filter and back to the oil pan. So when the engine is running there is pressure inside the canister. Oil is flowing out the canister and back to the pan. So filter canister is full when engine is first shut off. It is not under pressure. It will drain out the bottom of the canister over time and back to the pan. What you have is normal.
