The BA bag is a smidgen smaller because it is a quilt and has no backside insulation, but that certainly doesn't account for the differences in compressed volume.

I am guessing it has to do with the size compression sack they give you. Down is really able to compress quite a bit. I would be shocked if you could only compress that MH bag down to 10 L.

The question is do you want to spend the time getting the sleeping bag into the tiny little bag they give you. I personally don't mind doing that. But I can also see potential customers getting frustrated with not being able to get the bag back into its sack.