I believe this has more to do with projected sales than anything else - and that does not bother me, I hope they make millions. There probably were tech issues that delayed the original release date, but that put the DVD release within too close a window with the CD release. If the release of the DVD were pushed too close to the release of the CD, both would probably take a hit in sales. However, November is close enough to Christmas, that folks always find a little extra cash and justify a purchase they would not normally make or a purchase for gift giving.
Again, this is DT's livelihood, they should make their decisions based on revenue first but being careful not to fully alienate a loyal fanbase.