In one of the many secondary features on the Giant DVD I watched recently, someone said James Dean was not pleased with that scene, either. Dubbed or not, I found it sloppy compared with how good he was early on in the picture.
There were also a few good stories on the scene where he's offered money for the property Luz left him. He didn't want to do the scene because he had nothing to do, or so he thought. Then someone taught him the rope trick and with that, he turned a scene with little dialogue on his part into one in which all eyes are on him throughout.
Not a perfect movie, but a riveting one.
And I would love to see the musical staged. Of course, it has different scenes from the book in it. So, we know, for example, that Uncle Bawley, the character Chill Wills played, is likely gay, which would never have been addressed back when the movie was made.