No you are not quite correct.
The NP800 network protocol module is only used for Ethernet, WLAN and USB applications as you say, but it’s separate from the main digital streaming engine… it is separated by LVDS to help with electrical noise isolation, and is treated like one of the digital inputs into the streamer… essentially it’s a custom designed protocol bridge.
The core part of the streamer engine, the digital streamer board processes and controls the different digital signal feeds into the Streamer, whether they be from the NP800, SPDIF coax, Toslink, Bluetooth etc.
It is this digital streamer board that is controlled by the ARM CPU. It is this CPU that is ‘tuned”, if required, in software updates. This board undertakes the master clock management, as well as the digital audio signal processing… and conditions the signal for analogue conversion, or digital output by converting to SPDIF.
Therefore this software controls all streamer inputs, such as SPDIF, the NP800 network inputs etc… and any consequently software tuning affects the entire streamer operation and all inputs.
This also means software updates can equally affect digital audio and analogue audio outputs, and indeed I can attest to this.