"However, his playing in never robotic and he has a very definite taste and style of playing, creating lots of moods, colours and characters on his playing"
sounds lovely! wonder if you can attach an audio to your profile :)
interesting about his teacher's approach.
Yes, if you learn by listening, you must be learning to play that musician just as much as that composer IYSWIM. I don't think that's a bad thing...
I'm sure some music is hard to learn by ear - but most isn't. You do tend after a certain level to diverge between greater freedom for the musician to work out the content (in some genres) versus greater detailed notation of what is intended (Beethoven!)
I admit, the Chopin thing is something DS1's piano teacher told me... mind you, she does know an awful lot about the lives of the composers. But I'd better make way for any passing Chopin scholars....
Re the Richter quote: yes, that is one way of looking at music. The idea is that the music belongs to the composer. One person, and one person only (the conductor) is allowed to have some creative input in delivering it. But the music is an object - like a Greek Vase in the V&A - our job is to see who can revere it best. Apparently, Beethoven has a lot of responsibility for introducing this idea of the great master whose works are untouchable - there is a book called "music - a very short introduction" which introduces the history and politics of this kind of idea.
Alternative ideas are that music is essentially made in the mind of the listener - I absolutely love that idea! Philip Ball wrote a terrific book called The Music Instinct. It's really good!