The bug

This may be a clone of MC-174815, but this is a parity issue.

In Bedrock Edition, the piglins automatically attack the wither on sight, without the wither provoking them first. This is not the case for Java Edition as they behave differently.

To reproduce

1. Spawn a group of piglins and a wither in Java Edition
   → The piglins do nothing unless the wither shot first or explodes on them after being invulnerable.

Video (Java Edition)

Minecraft 20w18a - Singleplayer 2020-05-06 13-13-59.mp4

1. Spawn a group of piglins and a wither in Bedrock Edition
   → The piglins attack the wither without the wither provoking them.

Video (Bedrock Edition)

video-1588749820.mp4