Sugi,
Please don't get upset with me but I gotta get back up on my soapbox relative to our relationships with Service Advisors and Techs (mechanics).
If at all possible can you stay at the dealership and watch them do the work? As I've said before, where my cars go I go. I'm not suggesting that you stand back in the service area with your arms crossed and a scowl on your face the whole time looking over the tech's shoulder. Rather show the mechanic that you're a certified car guy and ask a few smart questions. Usually they are more than happy to share their knowledge about BMWs with you.
Another thing you guys have heard me talk about is befriending both the SA and Tech and using them exclusively. I trust both gentlemen implicitly and often take them some adult beverages in a gesture to say thanks for taking such good care of me and my personal car collection.
Yes, they were correct in driving your car to see if they bled the brakes properly. One of my pet peeves is a spongy pedal! Not knowing your dealership and the streets surrounding it, I can't say if nine miles is excessive or not. Is your dealership off a highway? Is the tech's only option to drive that highway which might explain the mile discrepancy. In know had I been you, I would have requested to be in the passenger seat during that test drive.
Thanks for reading. Just my thoughts!
DWP