Oil flow through the filter is controlled by a 1/16" diameter hole in the standpipe- - --at approximately the level of the inlet fitting on the side of the housing. That means that the housing will stay at least 2/3 full at all times. It doesn't even matter if the filter happens to be plumbed backwards- - - -inlet at the bottom and outlet at the side- - - -the static level of the oil with the engine stopped can never drain down all the way. The only exception to that rule would be after a filter change when the canister gets drained and cleaned.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!