This is due to the latest iteration of the Dolby EX flag. Early EX soundtracks (Phantom Menace comes to mind, but there are quite a few others) lacked any flag at all to identify themselves. In fact, many EX soundtracks were released without any indication that they including the EX data - they were listed simply as Dolby 5.1 due to fear of confusing consumers. A couple years after Dolby EX soundtracks started appearing on DVD's, Dolby added a new flag to EX encoding on new discs that would identify them to EX processors. The first batch of discs like this were Jurassic Park III, Pearl Harbor, and Atlantis. This flag did not necessarily force the EX processing to turn on. The current form of the EX flag has been around for probably two years now - that version of the flag does enable EX processing, and with at least some receivers (including the 1050) will not allow EX to be turned off.