I think that's the case for for lower-end restaurants, but for high-end restaurants, they are going to be tweaking things as they go. Ingredients are never perfectly interchangeable because they have to be grown or raised in real-world conditions that vary from one farm to the next or one season to the next.
Is this something that you know from actual restaurant cooking experience? Because high end restaurants lean extremely heavily on the concept of practice sessions where the cooks practice individual dishes over and over and perfect the mise en place for a specific menu ahead of time. Especially high end restaurants go out of their way to make sure that any experimentation will have been done ahead of time and not discovered at showtime.
High end restaurants measure everything both quantities, time and temperature extremely precisely and have strict quality control for the ingredients they use in order to ensure a consistent experience.
