You left out this part:
There wasn't a particular or exact thing we had to follow.
This is true. When someone says definitive, it means the only version that matters. Batman had several variations of his origin before Nolan. Most may point to Year One, but that doesnt make it definitive when most of it's original content is ever used as actual origin material.
I dont think that means Nolans is definitive, but he is right that there wasnt just one. He used several influences to create an origin instead of any one story.
The closest there is to deginitive would be the murder of his patents by Joe Chill, falling into the cave, the bats, and training abroad. When Bruce returns to Gotham that's where it gets murky. Most can agree that Gotham should be highly corrupted with Gordon as the only cop who wants to fix it. After that there's no definitive path to the story.
2020 aka The Grim Reaper Get Down.