In 21w06a, the height limits have been changed, with the low end being y=-64 and the high end being y=320. However, in the nether and the End, that change is not seen.
Expected: The height limit is supposed to be 384 blocks like in the overworked.
What Actually Happened: The height limit still uses the old system (21w05a or earlier).
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We're tracking this issue in MC-214796, so this ticket is being resolved and linked as a duplicate.
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