No matter what the center of the world border is set to, the Nether's world border center is always set to 0 0.

Steps to Reproduce:

[Step 1] Set a worldborder center at something other than 0 0

/worldborder center 1915 2865

/worldborder set 18000

[Step 2] Check the Nether's world border, world border boundaries follow if the center was 0 0 no matter what the center is set to.

Observed Results:
The Nether's world border center remains at 0 0 no matter what the world border is set to. All other dimensions follow correctly.

Expected Results:
The Nether's world border center should follow the Overworld and The End.

Notes:
I have attempted changing the world border limit and center multiple times, restarting the Minecraft server, restarting the OS server, behavior does not change.