Having experienced first hand the effect of “semantic diffusion” on the word Agile, and later even sprint and product owner – everything lost its meaning. I think he was spot on.
Agile existed in a vacuum as a manifesto, then it existed as a driver for cults/zealots of the ideology, then as a de-facto process, and now it's just watered down to something execs repeat when they want to say "our company isn't like a regular stiff corporation, but something more adaptable than that".
Agile should still mean exactly the same thing as it did in the manifesto - people over process, short cycles, adaptability.
You just described the same thing as the post, but the author went exploring the inner workings of why it happens.
On one hand, the original meaning of "agile" hasn't changed, as one could consider that immutable - and on the other hand, words do not have inherent meaning, they have usages.
I recall Dave Thomas (one of the signers of the manifesto) made the point: He points out "agile" is an adjective, "agile" is not a noun. https://www.youtube.com/watch?v=a-BOSpxYJ9M