Some mobs like creepers or endermans don't despawn on realms causing massive build-ups and occupying the mob cap
Steps to Reproduce:

1. Locate some natural spawned mobs on a realm
2. leave the area by about 100+ blocks
3. go back to the first area

Observed Results:
Natural generated mobs like creepers didn't despawn and are still there

Expected Results:
The mobs should have despawned according to the new rules

Screenshots/Videos attached: Pictures show natturaly spawned creepers after executing the /tp @e[type=creeper] @s. Same applied to endermans.

Notes: The mobs haven't been hurted, breeded or nametagged