Well, Ueshiba did sometimes use the term "harmonize", but much more often that's a mistranslation of the kanji for "Ai", which doesn't really mean "harmonize" in the sense that native English speakers usually use it.
Says who? I know of times he said so maybe even five times in one explanation.
No mistranslation. I don't buy this historian knows best logic. Historians gather data and should just give their data, which Stanley Pranin for example is good at. His opinion however or any persons opinion given to him is that only. Any conclusions drawn are coloured by the personal beliefs and understandings.
Kanji can mean this and that. One word can have many meanings. Mostly I've seen that just as a way of avoiding what he said because people including those there at the time didn't understand what the word means even if he was to print it on their heads. They can't relate it to what he did so he must mean something else type of logic.
Some or even much of what he said was either translated by someone close to him, in the same time as he was saying it and who understood English very well thank you very much. No looking back years later, no lack of understanding him as a person, no Kanji.
Finally, using Ai when I was explaining Ki and what he said about Ki in respect to harmony shows another misinterpretation in english let alone japanese. ( a response to Mikes view of mixing ki, blending,)