You are correct but drip aclimating is the least troublesome and the safest... I don't really understand your theory anyways because tying a knot in a tube and letting it drip into a bucket for a few hours is 10 times easier than coming back every 20 min and scooping out more water. There are other issues besides salinity that lead to shock... PH
levels, as well as am, nitrate, and nitrite (which should be just about void but not always). Also unless you are keeping them in the bag for hours and hours there should be more than enough oxygen to keep them alive. Most fish are shipped overnight in bags of that size.