Go to the following URL for a view of all BG transmission products.
http://www.bgprod.com/products/transmission.html
They make a lot of cleaner & flushes for various automotive components.
At the bottom of this URL is some info on their synthetic transmission fluid. They claim it's for all automobiles. I'm not sure what MB engineers would have to say about this.
It's entirely possible that your tech used one of their cleaner/flush products, followed by a refill of a more conventional transmission fluid.
Print the info at the URL and ask your tech what he did.
I'm not a big snake oil fan, but I can tell you from personal experience that this company makes first rate products. They have a fuel system cleaner known as BG 44K that will knock the snot out of your FI system.