You should have seen the sort of desperate expression on the face of practically any Asian I have dared to ask how she/he would define KI, be she/he of Chinese, Japanese or any other Asian cultural heritage. More so, when they were well into scientific thinking.
They simply did not use Ki as a defined entity, they had to add at least one other meme to this quite undefined "nonsensical" part, a meme in itself, and only then in this combination it started to take on "definite meaning".
So, looking for definite meaning in Ki as a stand-alone term itself seems to be a typical crazy western people predilection.
Reading through this thread what I found were opinions, if anything.
Don't know who you were talking to, I find it more western to think Ki isn't used independently. I was with a Japanese friend in his shop when one of his employees was grumbling and complaining. He just called him over and said"Today you bad Ki.....go home!"
They probably don't mention Ki or 'pretend' they don't use it as such when talking to those they can see from experience will not have a clue what they are talking about.
I don't go around using the word when talking to most but if they enter the dojo......ah, my world....standard.