If a block is placed next to an unloaded chunk on client, it won't be culled. This can be easily reproduced in spectator mode either if you connect to a very slow server and fly very fast or by setting spectatorsGenerateChunks gamerule to false and flying until you observe an ungenerated chunk.

Steps to reproduce:

1. Create a new world with commands enabled and gamerule spectatorsGenerateChunks set to false.
2. Set your gamemode to spectator and fly until you observe non-generated chunks.
3. Notice that blocks adjacent next to unloaded chunks are not culled.