I agree with you, Frank. The only writers I can recall at the moment who were able to reel off their writing almost perfectly on the first go with minimal or no rewriting are H.L. Mencken and John O'Hara. Mencken apparently did it as a matter of course and O'Hara did it and boasted of the skill. Despite the boasting, I believe him. There probably are and have been others with the same remarkable ability, but I do not know them.