I've never seen a bottle of Mercon or a bottle of Dexron, separately. The only thing I have ever seen is "Dexron/Mercon" followed by a roman numeral, depending on what the latest formula is and I've ran it in every transmission I've ever owned (all GM) up until I got my hands on a 4T60E, where I switched to Mobil 1. If it's available in some other way, then that's news to me. Type FA has been for fords as long as I have known. If there's something new, then that, too is news to me. I can't say I know a whole lot about the ford since I'm not on their team, so I won't debate you.
Are you saying you can purchase a bottle of "Dexron" or a bottle of "Mercon" - either one you want? Maybe I misunderstand you. The last case of ATF I bought was Dexron/Mercon IV, I believe. I run it in my 4L80E and my 4T60E. My 4L60E gets Mobil 1 ATF only.