Yu definitely came into Shenmue III with a strong on-paper plan and a wealth of old development documents and art to work with; if that's how we're defining development before the Kickstarter launched. Coding and assets though? Nah.
It's an advantage at least. Not a huge one, as there's always going to be a period of revision to make the vision suit the reality. Knowing what you want and how to make it is half the battle in game development, though.