Always respawning on the same block with no spawnpoint set

Seed: 3440635346844915271
World type: Single Biome, Wooded Badlands Plateau
Gamemode: Creative
After the initial spawn, when using /kill, I am always respawned on the same block (above ground, not the underground position of the initial spawn).
I made sure I didn't have a personal spawnpoint by using and breaking a bed, and I also manually set gamerule spawnRadius to 10 in case it was 0. Neither action had any effect.