Steps to reproduce:
1) Place the Warden in a hole so that it can not use melee damage against you
2) Punch the Warden and then take damage from a Skeleton
3) Die to the sonic charge
4) Look at death message: "Player was obliterated by a sonically-charged shriek"

How to see that this death message exists:
1) Let a Skeleton damage you
2) Run /damage @s 20 minecraft:sonic_boom
3) Look at death message: "Player 1 was obliterated by a sonically-charged shriek whilst trying to escape Skeleton"