pretty sure summoning a shield is only in one direction, and requires a great deal of dedicated focus and intent from the vortigaunt before the process of generating one can even begin. I imagine it would take a few seconds.
Shields are one direction as far as I am aware, never seem them put up a shield that covers more than 1 side. It also takes a few moments for a vortiguant to produce the shield. So I would agree with Flanders on this one.