No shit? Sorta like JFK by Oliver Stone? who'da thunk..
Of course the plot is fiction. And nobody knows what either man *really* thought of the other, as is the case re most of the famous and long-dead.
That does not alter the rightness of that scene - it is the reaction any serious composer would have, on seeing those 'drafts': Astonishment. Irrelevant to rest of the screenplay, nice romp that it was.
Jeez, do I have to argue the proposition that, "often fiction can express a truth better than a documentary?"
I give you then: Will S.
(if that Was his name. A work stands on its own, regardless of any putative bio of its author.)