JF you are right in a way. The bit about him having the actors in a room and having them improvise without saying a word himself. Definitely true. But he wasn't filming at the time. He would let them have at it and then construct the scene's script from there. So in essence I suppose you could say that his movies were basically based in improv. And I am sure that parts of his movies had the actors saying some lines that weren't in the actual script.
I know you know this, but I find it so funny how Peter was so frustrated with the lack of direction he got from John. Benny Gazzara tells a story of how Peter was so flustered during the filming of Husbands, and he asks John what he wants him to do. JC comes back with this long convoluted thing of what he wants him to do...and Peter is so freakin confused......and he asks Gazzara what he thinks JC wants...and Gazzara says..."he just wants you to sit down" I love it!!
That Constant Forge documentary is just terrific! It is so long, but it could of went on for another 6 hours as far as I am concerned!