There are two key details you are missing:

1) Its scalable to dishwasher size, ( enough to power a tiny house )

2) If you shot it with a bullet, it would just leak salt water. That is all. Lithium Ion will explode:

Now here is the quiz: If you have a cell phone that is inflating, do you A) Dunk it in water? or B) Toss it in a full document safe? or c) Quickly empty your document safe, and toss it in?

If a flow battery leaks, you can toss in a chicken into the delightful brine.

Since you cannot scale this easily to Utility sized batteries easily, the D.O.E. is not interested. i.e. if you are looking to scale this to a couple of hundred megawatts, just stop reading and thinking about this now. This is NOT mobile. Its not useful for cars or cities. Its right sized for homes.