I think you are missing the point of the gun. It's not a training tool for defensive work. It's a nice, lightweight high-capacity backpack piece, or a fun plinker. The mag release makes no difference. Even if used as a home defense piece, in what scenario is 31 rounds fired, with a need for a quick mag change? I'm not sure that .22 magnum is enough for zombies.
You may have a valid point. I don't see anyone using a .22 in this training video.
[ame="http://www.youtube.com/watch?v=KMEKKSmsVJs"]YouTube - How to Kill a ZOMBIE! (HD)[/ame]