It is likely an error in the SM, may be that page got mixed up with the A-S701 or some AVR that have some shared design and parts used, and those do use the TI PCM5101 or 5102 chip as well. There just don't seem to be any good reasons for the A-S801 to use a different dac for the optical/coax inputs.
For amps that have two zones and allows the user to use different sources for each zone then it might need to use a different dac for zone 2. That's what Denon, Marantz and Yamaha AVRs and AVPs do, but again, not for such entry level integrated amps. So, while I agree it is still clear as mud, but I think it is as least clear mud, that it is some sort of printer error. Keep in mind that Yamaha's integrated amp do share several of the ICs including volume controls, and circuitry with their AVR/AVP cousins, sort of standardization/or synergy, to minimize costs.
