9.h4 has brought White good statistics, but it's edgy, and not likely objectively best. As such it's vulnerable to home analysis. We may know soon whether that's what happened here. Nakamura succeeds in creating a dynamic position quickly, but in doing so gives away the White advantage by move 12. Interestingly, both players are serious French players.
The novelty in the game is 19.Re1. It's most certainly not prepared and probably won't enter into theory. By the time Nakamura plays 23.Rh2??, he's already on the ropes.