Because a) Super Hot = Naomi Harris, and Definitely Not = Tilda Swinton. b) Monasteries are co-ed facilities essentially never, and c) In the twenty-first century a government employee is more likely to be a minority female than just about anything else, whereas, in the 1960's she was likely to be white.
Mordo should never have been black, either. How many barons are there who are black?
As for the nonsense about "The High Lama" I haven't the foggiest idea what this writer is talking about. I have the Dr. Strange debut in Strange Tales #110 within an arm's length (between me and my kids it's in no shape for sale, so don't even bother to ask) and he is never called anything but the Ancient One in any of the books that I can recall. Sounds like a retcon, in addition to which there are no Dr. Strange stories before July 1963. (April, actually, but they post dated all of their publications in those days.) In particular, there is nothing I'm aware of in 1961.
Maybe someone is claiming some of the “tryout” characters in one-off stories from the “suspense”/”horror”/”scifi” comics that Marvel was publishing before they went with the superheroes.