Yes, I know it is a spec, like Dextron etc.
However, I have seen somewhere that the one oil is for brake bands and clutches, that require friction modifiers, and the other type is one for clutches and bands that does not require such. Which, as it stands, would make it impossible for the oils to be interchangeable.

I am getting to the viewpoint that all this is a sophisticated attempt to snare some money extra out of my pockets, and now I am determined to find out what is going on.

That Fords own branches here seem to disregards the requirement for Mercon oil in their own products, makes me wonder what is actually going on.