I just bought a Mityvac 7201 along with the brake bleeder attachment, which is soft plastic tube w/a ball valve on it. The directions say to plug the suction port on the 7201 that you would normally use to drain the unit, and use an adapter that comes w/ the bleeder. The adapter inserts in the hole on top that is normally occupied by the expandable drain plug. I checked and the tubing in the brake kit fits into the normally used suction port. Any idea why they would recommend using the adapter?