I should preface that I do not wish to provoke clashes of opinion.
So.
The keyboard must have its weight. Its right weight. Altering this downward weight is equivalent to falsifying the entire dynamics of the mechanics. Therefore, we will have a piano that is "more difficult" to play.
Fine, but the Maestro might say... "That's fine, but I don't care about the piano... what matters to me is the technique my student must develop..."
So.
I will speak specifically about piano technique and its development.
For now, I'll preview:
It is not true at all that one must "build muscle." Quite the opposite. Let's say that everything that develops strength and strengthens the flexor muscles and tendons removes sensitivity and does not develop the proprioceptive abilities of the brain, meaning it does not refine or educate those impulses that the brain must promptly "command" to the fingers. This leads to poor sound construction and difficulty in understanding how to achieve tonal nuances.
A healthy development of technique, i.e., the Art of doing, is one based on relaxation and the understanding of how every sound, group of notes, or musical phrase must be motivated. Only this leads far and generates a grand nervous energy. When we admire a pianist who has great energy and seems to make no effort, it comes from relaxation and full cerebral control of the "economy" of movement.
Therefore, in my opinion, there should be no weighting down of the keyboard. Technique understood as gymnastics, perhaps added to "weightlifting," does not lead far; on the contrary, it is often a string pulling in the opposite direction, in the name of effort.
Try to understand that every movement must be conscious and followed by our intellect. Insisting on gravitation and the holding of the weight of the arm and shoulder on the fingers—which must, yes, work with some articulation, but which must feel they can interact with the wrist, the arm, and the shoulder, bearing the bodily support; all with awareness and control of relaxation. I know, it sounds like something "Eastern".... but it is so. This is my conviction, which would need much different examples, which certainly cannot be provided in writing.
Videos will be released soon, I hope, on the subject.
No offense to those who hold a contrary opinion
Greetings
Paolo