A few ways to look at this, the traditional way of looking at the tint is that if there is a problem on the inside the police can't view inside. The problem is (and I have been on many responses to bank alarms) even with the windows untinted you can't get close enough to see what is going on. In fact the only real determination that can be made is that people seem to be coming and going out of the front door as if business is normal. If law enforcement got close enough to look inside the windows wouldn't you (and you do) get upset that the cops "came right up to the bank after and alarm."
I can tell you from many interviews with bank robbers that they do get close enough to look in your branches through the windows. They watch from the outside, in many cases, for a very long time before making a descision to rob your bank. I say this just to give pause not to rush quickly to a decision of what is or is not a best practice.