Yes, I picked up the lever. I went back there after a while, but then I tested it a few more times - and it happens every time. My version is 1.02.
...Okay, did a couple of tests. Observations:
1. This does
happen on the Humble version as well, the current one, at least. It might
have happened on previous ones. Presumably, I missed this.
2. Indeed, it doesn't matter when exactly you re-enter the room. As soon as you step on the trigger point, the movie plays, and even spawns another lever as a result.
Conclusion: the game doesn't flag the sequence as completed, so nothing prevents it from triggering again. I guess it's an oversight, because, technically, unless you forgot the lever, there's no reason to go back to this room at all. Come on, Pensil Test Studios, you can do better than that...