LOL! I had to do brew install iproute2mac so I can get the ip command on my MacOS.
Yep, when the Shark Jack is in Arming Mode and plugged into my computer, the default gateway is 172.16.24.1 and when it's not plugged in my default gateway is my firewall's inside interface 192.168.0.1.
http://sw-techgroup.net/images/ip-command-sj.png
http://sw-techgroup.net/images/ip-command-no-sj.png