Shooting down harmless missiles isn't a goal, it's waste. Furthermore, shoot and scoot is 101 for AD, as comromised positions are vulnerable by default (any AD can be overwhelmed, or leak).Assuming their claim that the S-400 managed to GTFO in time — doesn’t that prove that the system wasn’t able to counter C-400M? Isn’t the whole point of air defense to shoot down hostile missiles?
Finally, moving AD batallion can't shoot anyway.