I doubt it was just the opening scene, it was probably the entire film. It's just the opening scene is all we have to go off of.
That said, I would agree. While I liked the voice in the final film well enough, it just didn't sound right.. wasn't natural enough, sounded too much like amplified ADR (which is exactly what it was).
But in that opening scene is still far different from the rest of the movie. The rest of the film is a lot more grittier and muffled compared to the opening scene.