It's baffling how medicine can't produce accurate estimates. Sure, there are edge cases and differences between patients. However, every surgeon has a rough idea of how they're planning to do a procedure. They've been trained and practiced on it many, many times.
I have a torn meniscus. The doctor can happily tell me how easy it is to clean up and exactly what he'll do to fix it. He certainly knows what the risks are and potential complications.
Why he can't document that prior to surgery, I have no clue.