Funny, because I've always imagined quite the opposite. Ie. that it was done "live", as it were, and tidied up by AF to cut out all the "he said, she said" bits that would distract.

(Exactly like Ransome's 'Peter Duck', if you've ever seen the first few draft chapters. It had to jump back between the boat on the Broads (real life, where the children were inventing the story) and the South Seas (where the story was set). He abandoned that idea, and if AF ever tried that way of doing it, she clearly abandoned it too.)