Oh, I completely agree with this.
The aspect of this which I disagree with is the characterization of "composing by ear" as "harmonic thinking," which is misleading and not explicit enough. Not so much the term itself, but the way it is being used.
What is called "harmonic thinking" is just "using your ear" to hear the "harmonic truth."
It has less to do with harmonic rules or regulations. It is derived from the act of hearing, not rules.
https://www.talkclassical.com/blogs/...odel-part.html