Seeing the title, I can't help but thinking:
o/~
Where is bernhard, where is bernhard?
Here I am, here I am
How are you today, sir...? o/~
Bernhard and Chang are different people, who earned mutual respect. They agree on quite a lot of things. The one time I saw Bernhard disagree with Chang is about the exercise of the 4th finger while the 3rd and 5th are pressed.
Also, the tone is different. Chang has a physics + observing concert pianists (his daughters) perspective. Bernhard is into psychology + teaches basic work (NOT for concert pianists).
There is a way to summon Bernhard from the depths of oblivion. Simply post a topic that is both novel and interesting. I was able to do this twice, but I couldn't keep his interest long enough. They were non-piano flukes.
An interesting question is whether a non-pianist can ever properly train pianists. This might not sound so outlandish as the Williams' sisters' coach are their father, who has never been a professional tennis player. Did they succeed because of or in spite of him?
I'd guess... yes. Teaching is a wholly different thing than playing professionally. But of course you have to be familiar with what you're teaching. Think of all the coaches of athletes, and basic ed teachers. The "students" are often much better than the coach/ teacher.
Perhaps the question is not of "proper" or efficient training, but effectiveness? A teacher can have a good logical plan but that doesn't guarantee results. Or we could differentiate a "teacher" (for literacy and basic work) from a "mentor" (for long term and professional growth).