Java Edition equivalent of MCPE-155137.
The bug
Minecraft supports full 64-bit seeds. However, the End's generation largely ignores the top 16 bits of the seed, meaning that there are only 2^48 unique ends in terms of terrain and structure placement; very minor things can still seemingly vary, but not to anything near the expected extent.
How to reproduce
This can be seen in any two seeds that differ by an integer multiple of 281474976710656 (2^48).
Create a world with the seed 1
/execute in minecraft:the_end run tp @s 9914 62 9645 -75.5 -0.7
Create a world with the seed 281474976710657
/execute in minecraft:the_end run tp @s 9914 62 9645 -75.5 -0.7
Expected results
As these are completely different seeds, the terrain should also be completely different, even at the same position.
Actual results
The two seeds are almost a complete match, with seemingly the only differences being with configured features.
How to fix
All aspects of End generation that only use 48 bits should be made to respect the full 64 bits and produce results accordingly in the same way the Overworld does.
Further notes
When this is fixed, world blending should be enabled for the End as to avoid abrupt cutoffs with terrain generation changing.
Linked issues
relates to 3
Attachments
Comments 2

Strongly agreed. Should we pass this ticket by whoever assigned the other tickets a priority just in case?
Sad this got resolved as Won't Fix so quickly, especially since the related reports (nether, cave carvers and one that should arguably be split up into several reports), all about the same 16 bits getting ignored, getting a priority assigned.