The SACD audio is not available on the digital outputs because the music industry thinks we are all criminals at heart and will immediately make illegal, high quality copies using the digital information.

It's like the HDCP initiative in the video world, where high res video may not be available other than over DVI or HDMI channels where the info can be copy protected.

Note that if you have a copy-protected digital connection from player to receiver (eg. DenonLink) then you ARE able to output SACD over digital...