I would assume the BG ATF included with their machine flush is a low cost generic atf that meets specs.....why would they eat into their own profits on the trans service by using ultra premium fluids the average motorist either doesnt know the difference or even care...I would stick with the Mobil 1 atf or even step up to Redline D4,which I have been using in my 96Q with excellent results{original transmission operates like brand new with 228,600 miles on it}
Considering you have only 25,000 miles on your presently installed mobil 1 atf, if you are looking to save $$$$, skip the machine flush process and do 3-4 drain/fills using fresh Mobil 1 atf yourself using the drainplug provided on your trans pan...you can get 85-90% of the fluid replaced with multiple drain/fills.