I think you're still misunderstanding my initial post.
"Someone who actually has that kind of repertoire is just at a completely different level than most of us on the forums. Someone at that level could probably sight read a Chopin Ballade/Scherzo or a Mozart Sonata better than most our performances of these pieces even after we've studied the piece for months."
Like I've said before, I've never claimed that it'd be a great performance...just better than most students can do.
Also, my previous response was specifically directed at your statement that "nobody can pull off a great performance of a Mozart sonata by sight-reading it for the first time". Notice how I said "some"? Think of beastly international concert pianists (Richter, Ashkenazy, Barenboim, etc).
I bring the above up, because you state:
Well, they for sure have played Mozart. I never said they can't sight read a Mozart sonata, it's just so many details that it still won't be a great performance.
in response to my claim about "some" meaning any possible pianist. Notice how we're no longer talking about a pianist that has a similar repertoire as the OP and you're just simplifying and combining everything when there is a distinction.
The OP's repertoire is not that advanced (it is, but it is quite small). I really think that it's impossible to pull off a greater performance than one played by "us", who have studied the same piece for months. It's just... impossible...
The "us" specifically refers to the average forum visitor that plays piano - someone who hasn't even touched advanced repertoire. In other words, someone that isn't fully technically developed. Someone that has trouble sight reading and would take months (or possibly never) just to get the notes for a Mozart Sonata.
Also, see the underline:
"Anyway, my claim was that
a real pianist with the repertoire of the OP will sight read better than what most of us can do with a piece after we've studied it for months."
A real pianist (I must emphasize I am not talking specifically about the OP) that has Gaspard, La Valse, Don Juan, Petrushka, etc. in their repertoire would have studied exponentially more works than the pieces listed in their repertoire. If you had to write a repertoire list, would you include every single piece you've learned? Wouldn't you just include the works you're comfortable performing?
Put it this way:
Who would you rather hear?
An intermediate level student performance of Mozart
or
DMA Candidate from Juilliard sight reads Mozart Sonata