The reality is as Gonk states it.

Dolby and DTS didn't do an effective job of patroling and enforcing the EX/ES flagging and, as a result, there are LOTS of DVD's out there without the extra flag. Despite the claim of Dolby's site, I think they're still remiss in this regard to this day.

The best way to deal with it is just to observe what you're told the format actually is on the disk sleeve or in the audio setup menu on the disk and then set the 950 accordingly if it doesn't "see" a flag.

Honestly, this isn't such a big deal with the EX disks since that seventh channel is a derived channel from the differential of the two side surround channels. (Though you may hear a volume different due to some strictures Dolby places on the Cirrus -- or any -- third-party processing, as I've been told.) I often prefer the Cirrus processing of EX to the actual EX mode.

The ES track in DTS is a discrete track, so it's slightly more important to have it in actual ES mode but, again, in the real world, the Cirrus processing is nearly (if not equally) as effective. YMMV