Apparently, by some really lucky glitch, I got the "all sidequests fulfilled-use the Anti Annihilation Energy Agitator" by just using the Anti-Annihilation Energy Agitator. I can't be exactly sure now, but I think it happened like this:
Step 1: The 98% beta had a pre-existing glitch (just a flipped conditional or something in the game code probably) whereby all you had to do to get the expanded ending was to use the AAEA (whereas it should be AAEA+Fulfill all sidequests). This would have been fixed in the final build after the CE team examined the video and realized the error.
Step 2: FW recorded the final dungeon starting with the supposition that the AAEA was used, but FW hadn't completed all sidequests (the bartering and museum would have been edited in later after conferring with the CE team on what to do exactly -- I was pretty much figuring out everything in isolation, which is why this isn't as streamlined as it could have been I guess...like getting completely lost in the prehistoric forest maze).
Step 3: FW dumped the final dungeon video and realized that .ZMV corruption had claimed the first segment of the dungeon, and re-recorded and spliced it together with the previously recorded footage. In the footage that made it in, FW chose to go straight for the Time Egg and shatter it, but because the footage thereafter came from gameplay in which the AAEA was used, FW got the expanded ending.
Ironically, the only ending that I didn't catch of the endings that were coded for the 98% build was the non-expanded ending. Go figure.