Mobs dont despawn when hundreds of blocks away if you leave the area in spectator

steps to reproduce:

1. make an empty world with biome plains instead of void

2. create a hollow space, have mobs spawn there

3. tp 300 blocks away, there are no mobs now they despawned or at least unloaded

4. go back to the box and let mobs spawn again

5. now go to spectator and tp 300 blocks away

expected result: they should despawn

actual result: all the mobs are still in there loaded and counting towards the mob cap even though youre hundreds of blocks away