About the unchanged version, I've heard once it's because he wanted it like that: he really wanted to recreate the original Petipa version, which was similar to the Kirov one. It's what he did at POB for other ballets (Sleeping Beauty, Nutcraker, Swan lake....)!
And this is one great thing, we can see Russian soloist with POB when La Bayadère is performed in France, because the variations are quite the same (for season 2001-2002, Nicolas Tsiskaridze, as well as Svetlana Zakharova)
About the Makharova production, Nureev was considering it as a betrayal to the Kirov version because she changed lots of parts (golden idol variation was replaced by another one, she used some music arrangements, no fast part in the snake variation....)