I agree it all starts with the script. But the fact is writers in Hollywood are hardly ever valued properly. On Broadway, not a word can be changed without the writer's approval; that respect has never been officially part of the film business.
Well, of course the producer (Jack Warner) HAD his cut when it was originally released. That's why this all started. Writers hardly ever have a say. One of the few exceptions I can think of was when Friedkin redid The Exorcist ("The Version You've Never Seen") to please his friend William...
Hunt explains why in the interview above. The Extended Home Video version exists only on the blu-ray. The Theatrical version is essentially the dvd cut, which is what is now available in the DCP packages for theatrical exhibition. It's not referring to what was released theatrically in 1972.