I just read the article in full. Other than the child's pose and cobra, all of the stretches I listed fit with the suggestions of the author as the spine is not flexed. Same with the strengthening exercises. And with the cobra, I tend to focus on stretching my hip flexors and abs more than arcing my back.
I do find the perspective that bending is bad interesting, and my experience doesn't disagree with it. As I mentioned, I find that having a longer top tube and stem is better because I can elongate my back more, as opposed to curving it (which the author says is not good.) I am also very adept at rotating my hips forward when on the bike.