Oh, I don't think it's an especially good idea, I just think that's the notion behind it. I expect most of what goes on with these is marginally helpful in a real situation, at best, and few measures pass even a very generous cost/benefit analysis, and that's before you factor in psychological harm.

If this particular effort is effective, I expect it has more to do with discouraging shooters from firing in the first place (they may hesitate to "waste" shots on a window if they aren't sure people are behind it) or to slow them down. For exactly the reasons you note, I don't see it being very effective against someone who's decided that they definitely are going to shoot into that room.