In Japan, the character's name has always been "Ming-wu"; this is also reflected in the prototype translation.

Evidence is here: ????????? | ??????????? | SQUARE ENIX

Because Japanese cannot perfectly transliterate a name like "Ming-wu", this resulted in all the varying names for him such "Minwu" (Ming in Japanese is spelled more like "Min"), and "Minh" (The translator probably got confused and mistook the final "u" sound to be silent).

But then again the translators of Square in America probably had access to text detailing the characters' official names in Japan; they likely thought "Minwu" and "Mindu" sounded cooler than "Ming-wu"