I appreciate Sully's points. Particularly his last.
But I find the narrator to be full of crap.
If he had known what Bonin was doing (about 2:48 in)
Of course he knew, or could have known, without any reference to stick position. The Left Seat pilot has an attitude indicator. It is a primary reference instrument for instrument flight. Robert's attitude indicator would show him the nose was up.
DFDR evidence is that the nose was up, and that the attitude indicator for left seat was functioning.
Regardless of the position of side stick, the aircraft's attitude was wrong, and needed to be corrected.
Based on what I have read of the CVR excerpts, he did a few times suggest/direct to Bonin to "go down" or descend based upon the altitude obviously being wrong.
I never understood him to say was "lower your nose, that is why you are climbing when you should not be."
Can't say why that is how it went down, but I am puzzled at why a pilot would not do what I understand to be standard methods to assist the flying pilot with detecting and making corrections to errors or deviations.
How to Fly 101 was sadly missed by a professional pilot, in his role as co-pilot for that leg of the mission. Why that took place is a critical issue, as Sully notes at the very end of the video.
It sems to me to have to do with matters other than cockpit design, even though my preference as a pilot would be a set up like Boeing's. Or BOAC's boxing glove.
But there are some core issues here that cannot be solved by addressing that, such as
Basic instrument scan.
Basic error detection and correction.
Basic warnings to other pilot when outside of briefed/target performance goals (maintain heading, speed, altitude when in cruise flight).
The narrator cherry picks a bit of the entire sequence of events to present a skewed version of what the issue are. Note: I agree that stick position is most certainly an aid to the non flying pilot of what the pilot is doing.
I find his presentation dishonest and fundamentally flawed, even though he consulted with Sully and got some valid insight from an experienced airline pilot.