Editors DO NOT REWRITE. They guide and ask for rewrites, that’s all.
I get that.
But from what I’ve read the TKAM editor was much more ... Involved ... in production of the final product than was the norm.
As for the notion that Capote wrote TKAM, it's absurd. The man's ego wouldn't have allowed him to sit back while Lee was credited with writing a book far more successful than anything he ever did.