All I can see in those videos, as regards what the fingers are doing, is fingers going up and down on keys. Of course the player of the Liszt has much more precise control of how fast the keys are going down, but it doesn't look as if either of them is really thinking about the keybed much, if at all - nor do I when I play, the keybed is simply there to rest the key and finger on when they've finished doing anything useful.
I agree in the case of Prats, certainly. However, I think that a less talented player can make a huge improvement by initially thinking about the motion- in order to be in a position to forget about the keybed and get on with truly positive movements. I know that this is making a colossal difference to my own ease of playing. If you only notice yourself resting on the keybed between notes, that says to me that you're already dealing with the way the key lands upon it well enough not to need to notice. Not everyone has the ability to do it- even some rather advanced pianists. Just look at Leon Fleisher on film! Also, Kissin too often plays with shocking levels of impact. I seriously anticipate an early retirement from arthritis- just like Ashkenazy (another high impact player). The current post is primarily an introduction to the concepts- but the next one will be packed with exercises that illustrate how particular types of action enable totally unrestrained movement. I need to make various videos first, to illustrate everything very clearly, but I'd be interested to hear your views on the direct applications of the theory.
I see all the characteristics of redirecting momentum in the motions of Prats. There's no sign of him either trying to "relax" between notes or use contrary muscles to repress positive movement. Whether the other player consciously thinks about the keybeds or not, the movement is loaded with repression that suggests fear of them. I have a student who started with me recently at Grade 5. Although she plays rather well in many ways, everything is marred by an even greater type of repression. If I simply tell her to get into the keys and play more positively, that causes improvement- but she sometimes ends up digging in too hard and always tends to go back to less precise movements and thin, uneven sounds. With prompting, the quality always vastly improves- but this does not yet stick or become her normal way to move. I'm realising how important it is to show her a style of movement that can be executed with total confidence- without "keybedding" ever being a possible side-effect. Unless a student can be sure that even the most confident action directs energy away from the keybed (rather than into compressing against it) such consequences are always going to be scaring them away from the most positive style of movement.
Interestingly enough, I watched a little bit of a documentary on Prats where someone spoke of how as a youngster he was "never scared" of the piano. Very insightful, I think. The problem is that, for most pianists, they haven't acquired a foundation that would enable them to play with such lack of restraint- without suffering impact.