Also I can tell a pianist hand just by looking at it, usually the larger muscle at side of the hand connecting to the pinky and the muscle between the thumb and 2nd finger are the give aways. So there is certainly physical changes that occur to well trained piano hands.
If you press your 1st and 2nd together the muscle between the two will be noticeably more bulgy in pianists. I just googled that muscles name: abductor pollicis brevis lol, too complicated.
I can see physical weakness in hands when I teach my students but what are we supposed to do about it? It is not like we forcefully train the hand so it becomes stronger and more efficient, it improves over many years good practice, it is more a resultant rather than something you directly work on (too much directed forceful efforts can ruin your hands and set you up for a world of pain). I've seen all sorts of hand exercising torture tools but I think its a wrong way to go about it all, it may also encourage you to play with unecessary extra force.
I'm not talking about hand exercises, just regular playing of scales, other pieces, etc.
which would eventually "strengthen" the hand. But I'm not so convinced that a strong hand means much.
You may not encounter it normally, but I'm in a sort of situation where it comes up a lot. For example, I could play scales at 160 BPM and it would sound uneven. And then when I ask people, their answer is usually that it takes time for the muscles to develop, which is why you can't just play fast and even right away. If that is so, it is very frustrating.
And I can't find any consensus either. Taubman etc seem to deny finger strength altogether, for example. But I've also heard them say ridiculous things suck as to play all octaves 15. So, is hand strength real or not? Is playing the piano purely a mental (neuromuscular) activity, or is there an actual athletic component?
I used to think there was nothing athletic about it and that it was all technique, because I could play fast and loud and without strain for 6 hours without pain without ever actually training my hands in any way.
But I ended up with a lot of pianists telling me that the problems were elsewhere, and I didn't play things like they were meant to be played to compensate for a lack of finger strength.
And one should be careful before dismissing the advice of people who can play far better than you. And as someone showed me, "finger strength" does not equate to tension at all
Again, it may well be the case that what's being talked about here isn't literal finger strength, but it sure isn't bodyweight. Maybe it's arm weight -- I don't know.