if you do /setworldspawn on a floating island in an amplified world, then do /kill, you spawn below the floating island instead of on it. If you do /gamerule spawnRadius 0, then that fixes the problem only if there are grass blocks in the floating island directly below the spawnpoint. If it is on top of a different block (bricks in my case) then you would still spawn below the island.
What I expected to happen was...:
i would spawn on the island
What actually happened was...:
i spawned below it instead if the block below the world spawn was something other than a grass block
Steps to Reproduce:
1. make an amplified world with cheats (i havent tested if the bug occurs in other types of worlds)
2. in creative mode, fly up above the ground and use /setblock ~ ~ ~ minecraft:bricks
3. stand on the bricks and do /setworldspawn
4. do /gamerule spawnRadius 0
5. do /kill and you will respawn below the bricks instead of on it
6. now put a grass block on top of the bricks and /setworldspawn on top of the grass block
7. do /kill and you will respawn on the grass block. Basically setworldspawn doesnt work properly if there is no grass block
Can't reproduce the grass block changing anything. The world spawn being non-exact is intended though