There is no way that is the same saber. Whatever it was that was done to it, whether its the old one re-polished or a new one replaced it, or an older element re-used here, or combinations of any of them--it clearly has been visually altered in some manner. I'm gonna say its a completely different element than 1977. We know they were recomping all the other elements in those shots, and they didn't always recomp them in the same place or with the exact same element, especially since it was digital and they could do whatever they wanted. So it makes sense that if they were re-building the elements in that shot from scratch that the saber is a recomp of some kind. But as for whether that means every shot in the scene had a new saber is hard to say, I'm going by the caps here mostly. As far as I know, the seeker ball was recomped every time, and that would mean the lightsaber was as well, regardless of whether they visually changed it somehow as in this shot.