I don't doubt that they all get all the data there. SPDIF is not just data however; there is an RF frequency clock riding on that data which is really more of an analog signal as it is not the levels that are of interest but the edges (timing). At 2.8MHz, reflections, etc. become an issue. Really poor interface design, and the whole reason for reclocking schemes, ASRCs, etc., which do jitter reduction and make the DAC less dependent upon the transport timing.
And I should have said "One probable reason why I've heard digital cables sound different." since I don't use an external DAC and haven't personally gone thru myriads of digital cables as some I've read seem to do.