Wardens immediately dig away when spawned from a Trial Spawner with extra NBT data

Wardens immediately dig away when spawned from a Trial Spawner

 

To reproduce:

1. Find a Trial Spawner
2. Set the spawner to a Warden using a spawn egg
3. Switch to Survival

Expected result:

The Wardens should spawn normally like with a Monster Spawner

Observed result:

The Wardens immediately despawn