mob spawning not effective as of java

minecraft bedrock zombie villager curing and hero of the village offers now match with java but why is spawning not equal to java 

please fix this bug

i.e i made a dark box down in the overworld but it didn't spawn any mob even when I was between 23-128 blocks 

box in the end didn't spawn enderman even after packing all 4 sides and the top and bottom

slime chunks didn't spawn slime 

 

pls fix this mojang