In a world on Xbox One Edition, Ocean Monuments will spawn guardians around them and Witch Huts will spawn witches in them. When a world which had a witch hut or monument in it is converted to Bedrock Edition, guardians will no longer spawn around the monument and witches no longer spawn in the Witch Hut.

To Reproduce

Create a world on Xbox One Edition with an Ocean Monument or Witch Hut. Convert the world to Bedrock Edition. Run a "/kill @e[type=!player]" command to reset all entities. Wait about 3 minutes before running a "/tp @e @s" command to teleport all entities to your position. This is easier to see with Ocean Monument than Witch Huts, but you will notice that no guardians have been teleported to your position as none have spawned.