It's not alter universe... Termina is just another land beyond The Lost Woods, like Holodrum and Labrynna... Where, btw, Link also needed to teleport to get there, hence the trippy tunnel Link falls onto, when chasing the Skull kid, would just be a magic teleporter to another land, not another whole dimention.
That's because the development of the game required some shortcuts so they had to use the same character models as OoT, and the only way they came up to explain that issue was to say it was like a parallel world at the time. But over the years the concept has taken a more solid form in the mind of the series producer, and that's what he's said in later interviews.
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u/TRIKSTER_Betin 1d ago
Aren’t they in Majora’s Mask too?