Someone else mentioned a gold farm. Mine is over 128 blocks above the ceiling so that they can only spawn at the farm. I leave the farm and the new pigmen that spawn when I get in range of the closest spawn-able space down below the ceiling are aggro. I got off the server and someone got on sometime later and the aggro transferred to them. This is in 1.14.2 on a Vanilla Survival server.
Based on what you are saying and referring to what DrownedZombie said, you have the Bedrock Edition. This bug tracker is for the Java Edition. The bug tracker for Bedrock can be found here. https://bugs.mojang.com/projects/MCPE/summary