What I expected to happen was...:
The world would be deleted, and no audio from that world would play.

What actually happened was...:
Sounds coming from the world were still playing, even in the title screen.

Steps to Reproduce:
1. Die near a couple mobs in Hardcore Mode (Anything that plays sounds on its own works.)
2. Click "Delete World"
3. Once booted to the title screen, any sounds from the area you died in should still be playing, as if the world is still loaded after clicking the button.