The main thing was you could use Type F in anything, but you could not use Dexron in a Ford. Ford used different material (I was told paper based) in the bands, and Type F was used to keep them from burning up.

B&M Trick Shift that used to be $4 a quart when Type F was $1 was just Type F with blue dye instead of red.

I use Type F in all my 904's. I use ATF +4 in all my OD trans'.

Just a habit I'd guess.