I stumbled upon a very inspired performance (1949) of Chopin's Mazurka Op. 68 No. 2. And what I observed may offer a springboard of discussion on dimensions of piano technique.
I've been away from the Forum for while tending to a relocation to Berkeley, CA, my dream home. I love it here!

https://arioso7.wordpress.com/2012/09/29/old-world-piano-playing-1949-with-a-pronounced-wrist-break/

By "wrist break" are you referring to the movement where the wrist is lifting up and hand and fingers kind of drop down to some degree? Then when the wrist is lowered the movement is reversed and the fingers become more aligned with the forearm.

I have noticed this movement in a large number of(perhaps most) pianists with varying degrees of height and frequency. I think Valentina Lisitsa does it with a very high movement of the wrist although it doesn't look unnatural to me(some posters have commented otherwise). In the first video on your blog, the pianist seems to make this movement so often that it looks somewhat bizarre(not necessarily meaning incorrect)to me. I am very familiar with Morozova's playing having heard her in around five solo recitals and 25 master classes. Her motions as shown in the video you psoted look more typical of a normal use of wrist break.

Here's a video with Koji Attwood using this motion on a somewhat smaller scale(if I am wrong about this, please correct me! I don't want to mischaracterize anyone's playing)in a performance of three of his particularly beautiful song transcriptions:
http://www.youtube.com/watch?v=jk6ZiwFhd2w

Although I have noticed this motion in a large number of pianists, I don't know the idea behind it or why some think it's good or even required while others apparently think the opposite.

So I would be interested to hear other posters' opinions assuming we have agreed on what we mean by "wrist break."

This is a motion I rely upon to sculpt phrases in particular. I love the performances of the first pianist and Morozova. Both highly expressive musicians, with impeccable phrasing.

I teach the supple wrist right from the start of study. Before I relocated to Berkeley I worked on this flexibility with a 4 yr old who is now 5 and playing beautifully. She is now transferred to the hands of a Russian teacher.

I don't see how the wrist break, as it is being called, "serves" the music any more than a relatively calm wrist. Note : I did not say a rigid wrist!

Some may do this to keep the hand and arms relaxed, but the first example is so distracting I would not want to watch a pianist play that way. Any extraneous movements - and I do find those movements extraneous - seem unnecessary and certainly don't do anything to improve the sound or the expressiveness of the playing.

Regards,

I call that hanging the hand from the wrist.

Not sure what you mean by "sculpt phrases".

I think one can phrase the same way with or without this motion because there are great pianists who use it or don't use it (or something in between). It's possible that some pianists find this motion very useful or even required, but I'm hoping you can be more clear than "sculpt phrases", i.e. what do you mean by that term and why is the motion useful in achieving this?

I'd agree with Bruce that Czerny-Stefanska employs an extreme example of this motion, perhaps the most I've ever seen. If she uses that much wrist break in all her playing I would find it very distracting. OTOH she did tie for first place with Bella Davidovitch in the 1949 Chopin Competition, so she is a terrific pianist.

Chopin op.10/10, approx. 600 times..