Exactly.
No mention of rotation? There is no way you can talk piano technique without forearm rotation.
I wholeheartedly disagree. I think you can construct a healthy technique without putting any conscious thought into forearm rotation at all. In fact, what I see the most, is most students trying to consciously rotate the forearm instead of being supple and active in their fingers to do tremolos and other rotation-y stuff, end up tense and clumsy from this approach.
Also, the statement that the bicep and tricep raise the forearm struck me as wrong, or at least incomplete. The tricep opposes the bicep, so I don't see how they both lift the forearm, and I'm relatively sure the deltoid has something to do with it too.
The muscles that flex the elbow joint, according to wikipedia, are Biceps, brachialis, and Brachioradialis.
Since the body is an interconnected system rather than isolated things that move in some kind off binary on/off fashion, the deltoid might of course activate during certain movements of the forearm, but it is not in any way directly connected to this body part.
EDIT: As for the article, I have a lot of problems with it in addition to what keypeg said, a lot of things are unclear and could be misunderstood by the student. Some examples:
The height reached by the hand and the forearm during the negative-movement-stage will depend on the sound we are aiming to obtain from the instrument: the higher the hand, the louder the instrument will sound.
You can get a very loud sound from playing from the key too, no height required. You can also play pianissimo dropping your hand from shoulder height. The ideas here seem very limiting to me.
The targeting finger will act as a shock-absorber and a spring to re ignite the forearm upwards during the beginning of the negative movement (as soon as the forearm is ignited upwards, the biceps and triceps will take over)
I can see about five million ways a student could misunderstand this. And I disagree with the shock absorber part too.
The finger/s which needs to target becomes stiffer than the other ones which remain slightly lifted so they don’t impact on any undesired note in the landing.
Anything that contains the word "stiffness", apart from sentences warning earnestly against it, is dangerous in the context of piano playing, in my opinion. The fingers are better off being supple at all times.
All the weight of the arm is supported by the finger itself.
This can also be misunderstood in five million ways.