What harm are you expecting? Why would such a simple motion as very slowly and smoothly moving your elbows out to your side and then letting gravity ease them back in (all away from from a piano) do you any more harm than the countless movements you do in life?
The harm will be in habitualizing the tension in your shoulders caused by this 'simple motion' (both in and out). Once that happens you will no longer feel that tension - bad.
Don't be so bloody silly.
Don't bloody me! In Tai Chi (something I studied one-to-one with a master for some years) you are 100% conscious of the movement and stay that way. In piano technique you subsume any tension - your mind is on other things. So, as long as you're not sticking your elbow out whilst playing...
I don't think moving your elbow away from the body needs learning - unlearning perhaps.
the exercise (which you clearly have not read) is good for that too. It teaches how to do it in a very slow and gradual way, and to reduce the actual size of the movement- until the movement itself is virtually zero. However, a great many pianists have little sensitivity to how much they can vary the weightedness of the arm. This is the simplest means of getting beyond the idea that weight is on or off and exploring what a range of states is available.
In Tai Chi we would say empty or full and of course there is everything inbetween. Tai Chi is better applied to life itself rather than piano - learn to drink tea and brush your teeth with relaxed shoulders, that will transfer to every facet of living including piano.
However, the severe tensions in your Grieg video shows that this will not necessarily follow.
So you say. Just can't leave the ad hominem cvomments out can you?
I'm sorry that you take it personally, but I make these points of out of relevance to the subject. You said that Tai Chi necessarily spills over into relaxation in piano playing. Well, it clearly didn't even begin to in that film.
Obviously not 'clearly' as only you see it. Just can't play the ball, can you? (and you're certainly not sorry - God, you know how many times a day I hear that word at work? - it means nothing to me).
I will have nothing more to say unless it relates to the wider subject- rather than solely to your playing.
...a subject (my playing) only you seem interested in pursuing!
If that fingering lets you play with ease, is it "wrong"?
I reference your playing exclusively because it provides such a powerful example of how your cast-iron mentality can be seen to impact on your limited piano technique (or in the case of Tai Chi, how this has failed to have a notable impact on the results).