Mopar tranny fluid???

I'V Heard you cannot run Dexron III in a mopar tranny for one reason or the other.It'll burn the clutches out prematurely or clog the soleniods, and other various reasons.I don't get it,and don't agree with it.All Automatic transmissions are basicly the same,just shaped a little different.They all have the same elements, Aluminum cases,with steel ,brass and other materials that are the same in all of them (Raybestos,ect.ect.)..Tolerances and clearances pretty much the same,yet Mopar says you have to use their fluid all of a sudden.I just put a A500 together and in a 93 Jeep G/C,and filled it with Dexron III/Mercon,so we'll see.If anyone has another good reason this won't work,tell me,I'd like to know.