The film mix is noteably different. If you listen to the choir, when the strings come in at the end... it's quite different. Yes it's edited and layered in the beginning, and the percussive part may be the same recording, but the rest is not. My guess is that they recorded the percussive part (instrumental) separately... and then layered the other parts (strings/full orch), (Choir), (Ewoks) over it... I dont' think they expected to release it as they had... in what would create three versions, but there are now three:
1) Ewoks singing along and then choir takes over
2) Choir (album)
3) Choir film
Check out my set and listen to that cue and you can hear these differences. As for what it means by "Film Version Without Orchestration," I'm not sure.
I'd also read this page and check out the bottom:
Return of the Jedi