Steps to reproduce

1. In the nether, in the beta, fly around to various places.
2. /execute @e[r = 45] ~~~ say hi
3. /execute @e ~~~ say hi

Expected result

Based on changelog statements:

• In step (2) 15-20 monsters say "hi".
• In step (3) at simulation distances 6+ where spawn sphere is near full size, 70 monsters say "hi" (Java parity).

Actual result

• The results below will be skewed if you are in/near a bastion or nether fortress because of the abundance of structure spawns/spawn spots.
• Hoglins should be subtracted from Java results since they count toward the “hostile” cap in Java, but the “animal” cap in Bedrock.

  Range	Sim 4	Sim 6	Sim 8+	Java
  Step (2) / 45 block radius	8-12 monsters	4-6 monsters	4-6 monsters	???
  Step (3) / full sim distance	8-12 monsters	15-20 monsters	25-30 monsters	70 monsters

Bug description
In the latest beta the following change was mentioned:
"Monster spawning in the Nether has been changed to more closely match Java Edition (MCPE-65762)
There will now be a maximum of 15 to 20 mobs around the player in the Nether, instead of 30 to 40"

This change does not make sense after testing, since there can now only be up to 8 mobs in the nether instead of 16 of the Monster population group (See )

Related bug
Simulation distance 4
According to MCPE-65762, there are spawning way too many mobs in the Nether. The mentioned fix in the changelog was supposed to fix this bug, however the fix does not solve the issue in one way or the other.

Since the despawning sphere is so tiny (Mobs despawn 44+ blocks away) on simulation distance 4, new mobs tend to spawn more frequent and more closely to the player. The issue mentioned in the bugreport is about the mobs spawning too close to the player, making them overwhelmed by the amount of mobs. Reducing the Monster cave mobcap to 8 instead of 16 would still make this issue exist and doesn't change anything.

Ghasts
The bugreport also has a lot of duplicates to "Ghast spawning way too frequent". This change would not even fix that issue in the slightest, since Ghasts would spawn anyways, no matter how many mobs there are in the area. People would still be attacked in every direction by Ghasts.

Another issue with Ghast, which was also mentioned in a duplicate bugreport, that they would spawn in nether tunnels. There is currently a bug, like with Magma Cubes, where they can spawn inside 2-tall areas. It would be better fixing this bug than actually focussing on lowering the mobcap while Ghasts aren't much affected by it: (See Chri O' Briens comment about it https://bugs.mojang.com/browse/MCPE-65762?focusedCommentId=1016088&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-1016088)

Magma cubes
Also was mentioned that Magma Cubes spawn inside made nether tunnels everywhere. The change in 1.17.20.20 beta does not adress this issue, while it was mentioned multiple times in the bugreport that a lot of Magma Cubes would spawn there. The issue of Magma Cubes is that they can spawn in tiny rooms, even if their bounding box would align with a wall or ceiling. It is therefor better to focus on fixing this bug: https://bugs.mojang.com/browse/MCPE-46540, then reducing the mobcap in half.

Expected behavior
The Monster cavecap in the Nether is 16

Actual behavior
The Monster cavecap in the Nether is 8, making mobfarms even slower in the nether like they already were. A lot of people who make mobfarms would be affected by the lower cap, making their farms twice as slow, while the main issue here is not fixed

Proper fix
For the fix it is better to look at the mobspawning on simulation distance 4 and find a solution that would target only that simulation distance and not others. The simulation distance has a lot of problems regarding the small spawning range (24-44 blocks, outside that everything would despawn)

Another fix would be to get rid of simulation distance 4 entirely and focus on simulation distance 6. I hope most devices and servers would be able to run the small increase in loaded chunks, but this should stop any issues regarding spawning of mobs