And when I did the same thing, albeit accidentally, was it a glitch?
Like has been said, exactly what you are seeing is not exactly what he is seeing. If you sat there and practiced this for a very long time do you doubt you could also have a good idea of where to fire? The 88 AA is a proximity shell, so in my estimation it's functioning as it should. I have used the 88 AA to shoot at troops taking the town, iirc the M3 was enough to cause the proximity fuze to go off.
If the 88 AA is modeled to have its fuze ignite at proximity to enemy target then I would conclude it is functioning properly. You are saying the shells are going beyond the target, although I don't think there is a clear way of knowing that what you saw is what he saw, and that that is actually happening without looking (and knowing how to read) the code for the specific event.