With how this routes push notifications to an invalid IP, will they be resent or are they lost? When you put your phone is the box will you get all your missed notifications or just ones coming in while it's in the box?
Also your guests will think their phone is broken or your Wi-Fi is down.
I'm not well versed in networking, but this reads to me as it blocks and sends all notifications to the void and then while in the box the Pi allows new ones through.
The question then is do push notifications need an ACK and if they fail to receive one do they try again? I know cell carriers can tell when you're out of connection and can delay notifications and packets until you reconnect but this is slightly different.