Hmm, you are right about it being assembled from alternate footage. It's not the version Davis originally cut.

I guess that means that they found all the raw dailies though. Now, did they find the actual assembly negative? Maybe they did, but thought the alternate footage was better (this isn't a presentation of ROTE, just some silly footage for a blooper reel). Maybe they didn't, and that's why they had to use alternate footage. It's too hard to tell from a 5-second choice. But at the very least it confirms that the raw footage is at Lucasfilm and is catalogued. And I'm guessing the actual negative is there too--where else would it have gone? It was only printed once as far as I know (for Davis' VHS--probably it was also shown at the crew wrap party or something), so it's no doubt in the archives somewhere.