ya got it backwards...
the restored scene with them falling into the pit WAS redone by Peter Jackson and the WETA team, but it's an add-on to the release of this CLASSIC version on DVD that came out a couple weeks ago-
I posted on it...info is
at Retrocrush
interesting observation - the guys at WETA wouldn't tear apart one of the old models cause it was an heirloom practically, but they x-ray'd it - what surprised them were modified bellows for simulated breathing....they didn't expect to find that kind of special effects technology in it since it was supposed to work like a claymation device - LOL.
RB