Yup, though nobody I worked with saw it that way anymore.

There's a significant drift in its meaning, and there's also dissonance between different areas in the same industry. That's why I wanted to define how this jargon ends up used by me and my peers, and provide a reference point.

(There's a bigger point about value judgement -- I tried not to give too much negative or positive connotations to the whole yak situation, because I don't believe there's an objective mode for it.)

If someone claims to have coined a term but does not quite grasp its meaning, do you give them greater credibility?

More likely the author heard the term, made an assumption as to its meaning, and either misremembered its source, or it was coined and spread elsewhere.

I'm not sure what it means for the one who coined a term to not understand the term they coined. (At https://americanexpress.io/yak-shaving/ they are quoted as stating clearly that they coined it and attempted to spread it. Which need not be true, but if you're going to suggest that it's false, you'll also need some evidence.)