TC has a couple of public drivers (9 total) that is documented, but in addition to them it also has some specialized drivers that are not documented. The specialized drivers are generally written to handle exactly what the device or class of devices can do, nothing more. In this case it only supports serial, because all Atorch devices I have seen uses serial, i.e. not reason to add network.
The documented drivers generally supports more interfaces, because they have to work with a wider variety of devices.