No, what that is being stated is that, optical does carry the stream for surround, think of it like this:
http://forums.logitech.com/logitech...eakers&message.id=15700&query.id=37915#M15700
the last couple posts kind of clear up the confusion...atleast for me in regards to it.
I aswell have 5500 set up and get 5.1 under encoded audio files.
optical is capable of it, it just needs a DECODER and the source to have the file for it too decode....so justbecause you get a Stereo dvd or regular CD doesnt mean it will instantly turn it into 5.1
So lets say you get a dvd that has an audio options menu.
Stereo or 5.1
If oyu select stereo, it will output L & R channel feeds only, no matter how many speakers you have. so lets say on the z5500 you only have a stereo audio track/file/film...even if the sound is coming out all the speakers its just duplicated L&R stereo mixes.
now selecting 5.1
the control pod decodes the "wrapped" file on the disc/medium itself across the sound matrix (like stated above) to properly allocate to each speaker and through the proper digital decoding.
SO it has to be ENCODED on the medium (Dvd, audio-cd, audio-track, movie-file) so the decoder (Z5500 controll pod) can pan them out properly.
the optical is only acting as a LINK in the chain. or a bridge if you will.