Wither projectiles traveling through bedrock from the end to spawn

What behaviour is expected:

Wither projectile skulls stay and explode in the end when the wither is trapped in the center bedrock block of the portal such as in vanilla.

What behaviour is observed:

When attacking the wither the projectile skulls can travel through the portal to spawn and destroy the surroundings.

Steps/models to reproduce:

Create a wither in the end under the portal so that it's main head is in the center bedrock. Attack it and randomly the projectile skulls travel through the portal to spawn.

Plugin list:

No plugins

Paper version:

This server is running Paper version git-Paper-158 (MC: 1.16.2) (Implementing API version 1.16.2-R0.1-SNAPSHOT)

Anything else:

I discovered this on a server running git-Paper-147 (MC: 1.16.2). So I then tested on my servers running git-Paper-158 (MC: 1.16.2)
Also have tested this on my 1.16.2 vanilla server and cannot recreate this issue.

In the pictures, left half is the end and right half is spawn. I had set mobGriefing to false so as to not destroy spawn for the pictures. Attacks from players have the same results as attacks from iron golems.

Start by reproducing the issue on Paper 1.16.2 with a wither trapped under the End portal, then compare projectile behavior with vanilla. Trace the wither skull handling and portal-crossing behavior; done means skulls remain and explode in the End rather than reaching spawn.