Mobs summoned in Bastion Remnants won't drop experience balls after been killed. This situation affects Piglin Brute, Hoglin and Piglin, which are summoned with world generation in the Bastion Remnants.

Except these mobs, other mobs such as Ghasts can drop experience balls normally.

How to Reproduce:

1. use command /locate structure bastion_remnant to locate Bastion Remnant.
2. use command /tp to teleport here.
3. kill some mobs.

You'll find that no experience ball was dropped.

For Example: Piglin Brute

Killing Piglin Brute summoned in the Bastion Remnants won't drop any experience balls.

However, using command /summon ~ ~ ~ piglin_brute or spawn eggs can drop experience balls.