"A surprising amount of players have no problems with a DTS only track though."
Oh, I don't doubt that at all. It's just a soundtrack as far as the player is concerned. But DTS wanted their soundtracks to be considered one of the "minimum requirements", so that they could only put DTS on their DVDs. As we know, the DVD consortium said no.
I thought the DVD certification required stereo tracks. They have to have either DD or PCM, which is why DTS DVDs have one or the other (generally a DD 2.0, since it takes up the least amount of space.)
"Annoyingly, I think that the first "Mummy" film with Brendan Fraser did have an isolated score track on its first DVD release. Unfortunately, the subsequent releases have removed this (and many other special features)"
This is correct. I believe it was under the Languages or Soundtracks menu. If you let the menu play until the end, it started playing the isolated score. I have this DVD, and enjoyed listening to it from time to time.
I believe the reason this was changed, and why many DVD's don't have this anymore, is because people won't double-dip and buy the CD soundtrack.
Not to mention they don't always pick the best films, either (Panic Room?)
Even though I love Fifth Element, I haven't bought the SuperBit because I don't have DTS. I would love to get Labyrinth and Dark Crystal as well (and the more expensive special editions also - I love those films! )