I think I found the answer of my own question in the manual:
[quote]At 44.1kHz and 48kHz sample rates, you will only need to use 1 optical port for
all 8 channels, with the second port simply acting as a duplicate or split. At
88.2 and 96kHz, you will need to use both optical ports in order to access all 8
channels as higher sample rates will limit the channel count to 4 channels per
port.[/quote]
So if I read this correct, at 44.1/48kHz the second port acts as a duplicate (or split - whatever they mean with that), which is exactly what I want. That’s great!