The bug

I found a weird quirk with the way chunk rendering works. It seems like chunk rendering is a lower priority for players in spectator mode than players in Creative mode even in singleplayer. This is not caused by the spectatorsGenerateChunks gamerule as it can be observed in a freshly-made world without any changes to gamerules

Steps to reproduce

1. Fly around at the max speed (using the scroll wheel) in spectator mode
2. Find a spot where the chunks fail to render even though they are loaded
3. Switch to Creative mode --> Notice the chunks that weren't rendering suddenly render way faster
4. Switch back to spectator mode --> the chunks that started rendering stay rendering

Expected results

Switching gamemodes doesn't affect the speed at which loaded chunks begin rendering

Observed results

Switching gamemodes changes the speed at which chunks render