Setting doMobSpawning gamerule to false doesn't prevent chunks from being loaded with entities

Chunks are loaded with mobs in them although the gamerule says otherwise..

How to reproduce:

• Click "create new world"

• Click "gamerules"

• Click "true" besides "allow mob spawning"

• Create the world

• Execute /kill @e[type=!minecraft:player] until it says "no entities found" (should say it on the first execute, doesn't due to the bug)

• Move and load new chunks

• Execute the command again: new mobs generated

• Type /gamerule doMobSpawning: it says it is set to false.