No one knows. It looks like a new transfer.
Possibilities:
-1977 negatives. IMO doesn't look this good though.
-1977 separation masters. I doubt they would scan and composite three different film pieces.
-1977 print masters. Possibly, if they were stored correctly. Would explain the gate weave too, due to shrinking.
-1977 IP. My impression was that these are worn to bits, and the start of the film tends to be more worn due to handling. But could be a possibility.
-1977 Technicolor prints. Another possibility, but IMO unlikely simply because this was something Lucas had printed for himself and kept in his home.
I am guessing they just pulled a print master out of an archive. But who the hell knows. I mean, if they took the original negative and did a standard-def scan who is to say that it wouldn't look similar to that? Where and most importantly when this piece came from has always been a bit of a mystery to me. The crawl appeared in Empire of Dreams but it is clearly a separate source of some sort. Maybe they re-compressed that original scan for the doc, but the footage found there does look like it is a totally different source and/or scan, however, it really is a big coincidence that the first time this was ever telecined was for that doc and now here all of a sudden for a release that only had to use existing materials it was included. So who knows.