> I interpret it as the former requiring the creative fireworks of youthful neural elasticity and the latter the depth we associate with lived experience and wisdom.

That being said, I think an interesting factor would also be which of those who wrote major works in their later age already did a decent amount of writing in their earlier years. Even if you have life experience, I would imagine that you will have to build up the "muscle memory" of writing skills in your more elastic years (e.g. by becoming a successful writer after a lifetime of journalistic work or just minor literary works).