i have a two quart A'sump, if i turn the motor off at about 60 psi at the engine, and about the same on the air pressure gage on the end of the A'sump, then later toggle the cold
oil to "pre-lube", my Windsor motor will rise to about 20+ psi, and stay there for awhile, then slowly bleed down the pressure.
My guess is that if about half of the A'sump's
oil is discharged immediately into the
oil lines and the initial part of the engine's oil gallery, that would halve the oil pressure at the engine (about 25 psi) immediatly, then it bleeds down.
Mine does exactly that, so i think you are fine.