Then he has a setting wrong somewhere and it's telling the player to pass the sound straight to the TV rather than it being decoded and processed by the amp.
Most likely he's trying to send the receiver Dolby HD or DTS HD sound, which IIRC the 463 can't handle, so the sound is going straight through to TV.
If his player can't decode these soundtracks and output them as Linear PCM over the HDMI, which the 463 can handle, then he may think he needs the optical cable. But most players can do this, or at least output the standard Dolby Digital/DTS soundtracks over HDMI, so he probably doesn't need the optical output.
You won't have any such problems - if problems they are - with the 863SE.