Well, maybe they should have dropped psionics as a power source and called everything ki then?Particularly given that that form of fantasy story pre-dates western "psionics" by centuries, if not millenia.

...mhm, I'm not sure I agree. It depends a lot on what you think 'relatively recently' means. Compared to Illiad and Beowulf? Then, I agree.I also question the wisdom of a taking psionics and removing the anachronisms. There's been mental magic in myth and legend for a long, long time, but "psionics" in any sense of the term was a revision created relatively recently and set in direct opposition to regular superstition and magic. It was a "sciency" vision of magic that was supposed to be "actually real" by those who pretended to practice it, or who popularized it. Taking it and then returning it to the medieval age just doesn't quite work for me.
The line between fantasy and science-fiction is not well defined. Many authors don't even make that distinction, simply calling both speculative fiction. Magic and psionics were often used synonymously.
Imho, psionics in D&D always covered a lot more than the sci-fi/new-agey concept of psionics. Imho, monks fit well into the psionic power source if you look at the less flashy psychometabolism powers and maybe some of the psychokinetic and personal telepathic powers.
Then again, I don't quite see why monks couldn't simply have been a martial class. Many of the martial powers have a strong supernatural feeling to them, anyway.