Very interesting question Adrian!
Though absolutely not on the level of those players mentioned, if I may, I'd like to humbly contribute something from my own perspective, since I'm performing a lot more now. If interested, some details are here:- http://www.classicalguitardelcamp.com/v ... 6&t=112260
I have to admit that when I start learning a new piece, I immediately get preoccupied with phrasing, tone colours, dynamics, etc. - from the outset. The "mechanics" of my hands get less mental space.
However, some years back, I was asked to stand in, for someone who couldn't play part 3 in a trio. I only had the music two days before our first rehearsal, so I thought I've just got to get these notes down as quickly as possible. My usual approach went out the window. At that rehearsal, one of the other players, who had a postgraduate degree from a conservatoire, said, to my surprise, "I'm amazed you picked up that music so quickly - I couldn't have done that."
I think there may be a lesson in that for me! For when I perform, I rarely do so flawlessly. However, this doesn't seem to matter to many people. Even so, I certainly perceive, rightly or wrongly, that these days, some people make negative judgements of my playing because I'm not 100% accurate.
Personally, at least for me, I think it is an issue about emotional engagement and being more right brain orientated. I hate maths!
I'd like to share, if I may, that I was amazed to received a wonderful mention by Jason Vieaux, once, who commented that my playing was very poetic and I had a deep commitment to the music that was deeply felt.
“Do what you can, with what you have, where you are”. Theodore Roosevelt