Roger that.
Poor operational procedures can result in fluid transfer (i.e. selecting the park brake with A system pressurised but not B system).
One thing puzzles me: on the diagram I see the Parking Brake valve is on the B return line.
If Normal brakes and Alternate brakes are two separate systems, is it possible to set the parking brake using Alternate Brakes ( B pressure not available)? Is there a Parking brake valve on the A return line?