The /setworldspawn command will appear if it has succeeded if ran in another dimension, but only actually works in the overworld

When reporting bugs against version 1.20.6 please make sure you have actually tested in version 1.20.6.

I can see that this was fixed in 1.20.5, and the translatable text was added:

"commands.setworldspawn.failure.not_overworld": "Can only set the world spawn for overworld",

Attempted to reproduce it anyway:

the_nether:

/execute as @p in minecraft:the_nether run tp @p 0 100 0
/setworldspawn 0 100 0

the_end:

/execute as @p in minecraft:the_end run tp @p 50 60 50
/setworldspawn 50 60 50