1. This bug does not affect Vanilla.
2. The bug was tested on both CraftBukkit and Spigot.
3. I did not find any reports about this bug.
4. Only 1.15.2 was tested, as the gamerule in question is not present in older versions of the game. The bug occurs on both CraftBukkit and Spigot.
5. Steps to reproduce:
   1. Run a fresh server with the reproduction plugin linked below.
   2. Enter the server.
   3. Use the command /step1
      1. This will set the gamerule to true on "world".
   4. Use the command /step2
      1. This will kill you.
      2. You should respawn immediately.
   5. Use the command /step3
      1. This will teleport you to the spawn of "world_nether".
   6. Use the command /step4
      1. Expected Behaviour: You should see the respawn screen.
      2. Actual Behaviour: You respawn immediately.
6. Not a behavioural bug.
7. Reproducer Plugin included below.

Time Spent: Approximately one hour.

I'm unsure if this affects other gamerules. This issue was reported to the Multiverse team, and I was able to reproduce it with both Multiverse and Hyperverse. So I believe it is a Bukkit bug.

Please see this comment and the one that follows it for related behaviour.

Reproduction Plugin Source: https://github.com/nicegamer7/GameRuleBug