Okay, so some of them are obviously test dungeons used by the design team to make sure things are working, those would be the beta levels in the second video.
The first one, however, seems like it contains unfinished, prototype dungeons.
I always said WW was too short and too easy.
I think I remember Miyamoto saying that there wasn't enough time to complete all the dungeons and that they were going to carry the left overs into the new Zelda game, which would be Twilight Princess.
I hope so, I'd hate that game to be as short as Wind Waker, Triforce treasure hunt included, or as easy.
Anyway, look and discuss and, if you have an Action Replay, play.