Spell Shield doesn't work?

[Embolism]

I thought spell shield is meant to protect you from most hostile action, e.g. getting shot at by a gun. Apparently it doesn't.

Butt Collector is encased in a protective shield.

Oddball Stroble fires Riot Shotgun at the floor!

You start bleeding!

Butt Collector's shield deflects the shot!

Butt Collector screams!