That is one reason I like the old volvo's. The upper and lower gear cases are using the same fluid.
The other benefit from a drive shower is no more white chalky deposits building up on the outdrive.
Are there any drives that DO NOT share fluid between the upper and lower units?
That would be THE benefit of the drive shower. When the drive gets hot and is dunked back into the water it flash boils and leaves the deposits. Keep the drive cool with the shower and no boiling, thus no deposits.