You live in a very comfortable world in which the results completely and infallibly reflect the amount of work you put. But any realist knows that is far from true. For one, the legends are hardly known to practice even approximately same amount as each other; some were practice hogs and some practiced no more than 2 hours a day. This alone should be enough evidence disproving your ridiculous claim. I personally know many pianists who are far more committed to piano than I am but are, somewhat objectively, inferior pianists.
I expressed myself in the wrong way
I too don't believe it is just so proportional to the effort
But you're wrong too into stating the difference is due to inborn characteristics
There's so many factors at play and clearly the ability at the piano is multifactorial
I don't believe in inborn predispositions (and never seen any scientific proof of them) but I believe there are lot of factors which are impossible to control and judge that make each piano playing/learning path unique
For example when I was 4 I saw Fantasia by Walt Disney and got absolutely enchanted by it and kept watching it and even recorded the soundtrack after asking my father to buy me a mic. It's a rather small event but maybe if it wasn't for that movie I would have never "awaken" my music sensitivity and would have never started taking piano lessons
Education means ex-ducere; literally drawing out
Therefore educating is not introducing notions and ideas in the brain box but finding that experience that draws out what you have inside, that triggers the growth of something that remains in the embronial stage for many. I even accept that a mother listening to lot of music while pregnant and the fetus perceiving it may condition again the musicality of a person. Then of course a lot of factors determine whether you can grasp better the whole concept of harmonical and melodical construction hence making it easier for you to learn new pieces. For example it is well known that what makes learning pieces very easy is "mindful practicing" rather than just X amount repetiting X piece over and over
But again the level of mindfulness is influenced by some many factors
One can even make a case for analytical thinking propension or analogical thinking propension. But again it is well known that developing one over the other is just a matter of life circumstances, choices, experiences and billions of external factors but it's not a matter of inborn tendencies. Desterety too is influenced by billions of factor
For example certain activities or sport or drawing may create the basis for making piano playing easy. No one know and no one will ever known. But again desterity if not unborn
There's a very good book by the genetists and biologist Lewontin (The Triple Helix) that make a case against the belief that genetics and inborn tendencies influence in a predictable manner our life. He makes the point that humans without the environment don't exist. There would be no human though processing or consciousness without an environment, if we just were born in the blank. But he also makes a case that it will always be impossible for science or any other field to observe and known the factors at play
Each factor influences another factor wich influences another factor which goes back to influence the first factor with creates new influence paths all over it.
We're talking about millions of billions of new/changing/transforming/mixing impulses and imputs per second worldwide. Even grasping the 1% of this would be impossible
The issue of nature vs. nurture is an old one and nurture won
It won because all the studies attempting to prove that there's a natural pattern in behavior, choice, skills, attitue always failed. Instead people kept reacting and changing according to their circumstances. It won also because the advance is sociological and anthropological studies have showed how there's nothing culturally universal.
Everything is indeed relative because even things that we give for granted like being male or being female and what it entails is culturally constructed and not universal
The biggest evidence is how the people that have completely different habits, though processing, role consciousness, ethics ... share with us an identical physiology and neurology.