The wampa scenes were never in any cut. For the simple reason that they were never completed. There was nothing to cut out in the first place because they never had a scene, just a few isolated shots and inserts. I don't even think they could "finish" the sequences with CG today, because when they realized it wasn't working they abandoned it, so they left out more than just a couple of Wampa inserts, there is significant live-action portions as well.

Regarding the assembly cut, there actually are a few references to cutting in Once Upon a Galaxy, now that I think about it, nothing too detailed but a few asides. Towards the end, Kershner started cutting the footage he had shot. He says that at first he didn't even want to show Lucas dailies and wanted him to wait for the rough cut before he saw anything; but then (and probably hastened by all the production delays, in truth) he decided to send Lucas dailies and also allow him editorial input as they cut it. I'm not sure if this was after or during shooting though, you might find out if you skim through the second half of Once Upon a Galaxy.