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There is approximately one quart of motor oil that does not drain from the engine because it is trapped on the tray containing the connecting rod oil troughs, and some is trapped in the valve chamber. The dip stick does not indicate the trapped oil. So only 4 quarts of motor oil are necessary for an oil change.
However, with 4 quarts of oil in the pan, I find with both of my Model A's having Model B engines, the motor oil will leak until the level is about halfway between the L and F marks on the dip sticks. This indicates that more than 3 quarts, but less than 4 quarts of oil are necessary for an oil change. My practice is to pour-in the 4th quart until the oil level on the dip stick is about 3/4 of the way up to the F mark.
For an active Model A or Model B engine, there is always motor oil in the valve chamber, so the main bearings and camshaft bearings will not
run dry. Without this trapped oil, the engine would likely start with inadequate oil feeds to the main and camshaft bearings. So the Ford engineers intentionally designed the A & B motors it to have trapped motor oil.
The exception to this dialog is the engine that has been in storage or on a first start after rebuilding or overhaul. To assure there is motor oil in the valve chamber and oil pan tray, one quart is poured down the distributor's hole. This fills the valve chamber directly, and it fills the connecting rod troughs via the overflow tube.