That's funny. I can't imagine what would be in ATF that would react differently. The guys at my AAMCO place told me there is virtually no difference in fluids that the transmission is going to notice.
Interestingly, Ford and Cadillac both used Type A fluid in the 1950s and 1960s.
When Type A fluid was more or less discontinued, Cadillac went to Dexron and Ford went to Type F. Yet, today, you won't get any Cadillac people to put Type F in a Hydramatic transmission or a Ford guy to use Dexron in a C-4. Why not? They both were originally designed to use the same fluid, Type A.
AAMCO dude told me they use Mercon V in virtually all their rebuilds.
And how about the old timers who said that no automatic transmission ever shifted right after 1972 when whale oil was banned as a friction modifier!