Simple explanation: The wonderful folks who did the work on the DVD
were too lazy to actually transfer the real stereo mix for the songs over
to the DVD to they simply put a surround sound automatically downmixed
to stereo version on the disc.

Need proof - Listen to the infamous snare trip echo that's only on the
surround sound mix of "Can't Stand Losing You." The original stereo
mix doesn't not have this annoyance. Also on the surround sound mix
of "Every Breath You Take" the backing vocals towards the end are
anchored directly to the rear speakers with no ambiance towards
the front.

In other words - Universal screwed up yet another DVD.