Companies buy parts based on the manufacturers’ specs, assemble them and sell a product that they don’t know all aspects of its performance. There have been many cases of products that went under because the seller of the final product did not (and could not) know how the final product performs.
There are other aspects of DVD players that nobody was ever able to explain to me. I have 2 players connected to the same DAC1 through their S/PDIF jacks. One is an old Panasonic S55 and the other a Denon 2910. The Denon gives me much better sound from DVD-V's, but both sound the same for DVD-A’s and CD’s. How come? It’s all zeros and ones, no? (Assuming jitter is not an issue because the DAC1 resamples and corrects jitter.) Someone suggested that the explanation is that the DVD-V soundtrack is compressed, lossy, multi-channel audio data. The Panasonic and Denon probably have different types of circuits to expand/extract that data to 0s and 1s before pushing it out to the DAC. The difference in the sound probably lies there, and the fact that the Denon and Panny sounding the same when playing DVD-As and CDs makes complete sense. They're only transporting the 0s and 1s to the DAC, that's it.
The problem with that explanation is the few audio-DVD’s that I burned myself with audio-DVD creator are uncompressed and yet they sound better on the Denon. I don’t believe I will ever find out why, because Denon and Panasonic (and everyone else) buy the circuits to expand/extract that data from DVD’s from third parties and they don’t know exactly how they function. These are not questions that someone can just look up; I believe it requires real research and some serious testing.
Noam
This is how they responded to my e-mail:
Noam,
We have heard conflicting reports about the audio support through optical and coaxial. Our manufacturer partners and reviewers have said that we dither to 16-bit, while end users and beta testers claim to receive 24-bit through optical and coaxial. Our official statement is 16-bit.
How could they not know? 
Probably just some L1 guy sitting there answering emails... you may be able to push back and get to an engineer type who would actually know the answer.
