Over here some carriers will even sell you a static IPv4 address for your cellular connection. Other than that, packets are packets, this shouldn't be very surprising.

His blog is hosted on the modem but it does not actually use the cellular network, he routes traffic back to the host using adb port forwarding and then to some other host via USB and then to the Internet.

This isn’t going over the mobile network if I understood the post correctly.

The server is connected via ethernet over USB. But the server is running on the CPU of the GSM modem!!!