I was told by a collector of SW toys to maybe check "The Making of TESB" pocketbook & read the GL interviews for more info. to see about BASED ON THE NOVEL etc. I can't because I still don't have it. It may not be necessary now after zombie84's confirmation (thx), but it may be nice to know what the reason was if it is explained because the 1st. 4th draft also has it as well on the one up at eBay now.
I was also told that most of these original production scripts actually got sold off (not auctioned) starting roughly Summer-Fall 1980. The SW fan club was given first shot at them & then they appeared in small 1/8th sized page ads (bottom of page & near the back the mag.) in the popular sci-fi film magazines at the time in the U.S./Canada (not sure about the rest of the world) until the scripts got sold out. He thought that he likely saw the ad. in STARLOG magazine (Anybody have some issues from this period?) about that time & maybe others like HEAVY METAL or even a science mag. called OMNI. A few were autographed & more expensive, just like this 1st. fifth draft listed on eBay.
The typing mistake on the draft could easily be explained. It's a typing mistake. I'm guessing at this; but in 1979; if GL came up & told you to type 600 copies on a typewriter by Thrusday I'm sure a few mistakes could get by you. I doubt it was put on any mammoth computer at the time for printing as George was paranoid about security leaks.
I wonder if this is included in the package:
February 19, 1979
Correspondence from Irvin Kershner to George Lucas, regarding revisions to pages 143-160.
Source: Bouzereau: p. 123
I see on the sample page 02/19/79 is on the corner.