the camera would do a stop down metering and adjust the shutter speed if the aperture isn't the correct aperture.
That's correct. The silicone cell is so fast, it reads after the lens stops down. That's why you can even use PRE-MC Rokkor lenses on the XD and X-700 cameras in S and P modes -- as long as they have auto-diaphragms.
Minolta could have put a P mode on the XD cameras, and an S mode on the X-700 -- but didn't.