I don't know what the implementation is, exactly, but "tivoization" prevents modified binaries from running on a given set of hardware. The Pioneer box is changing the hardware behavior (disabling analog output) in response to the type of input it is getting, with no apparent reason for doing so except the rights-management paranoia of content producers....who in this case have no interest or stake in the specific content being transmitted.

I believe the content producers would like us to all have speakers with amplifiers built in, which take digital signals with copy-protection. That way nobody can hear anything unless Sony et al approve.