Both the digital out and analog out output are duplicated signals from the outputs of the DSP structure. As you can see from the plugin/datasheet/manual, the SHD has a 2x4 DSP structure. One of the stereo source (RCA/XLR/USB/Ethernet/TOSLINK/SPDIF/AES-EBU) is fed to the SHARC DSP processor. Does its magic and 4 x processed "outputs" become available in multiple formats.
In other words,
OUT1 = RCA 1 = XLR1 = SPDIF ch1 of the SPDIF 1&2 connector = USB recording ch1 (inside your OS)
OUT2 = RCA2 = XLR2 = SPDIF ch2 of the SPDIF 1&2 connector= USB recording ch1 (inside your OS)
and so on...
While we're on this topic, a related questions we get is: "Can I get 6 ch outputs from the SHD for a 3way crossover".
(E.g. 4ch using analog, 2ch using digital).
As you can see from the above, the answer is no. With all outputs being duplicated it's not possible as it remains a 2x4 structure.
To sum it all up, even if the SHD does have lots of connectivity to allow your system to evolve and remain flexible, it remains a 2x4 platform. 4 x processed outputs.
Hoping this clarifies it all for you.