According to exhaust velocity theories, this is true, however I like the straight through mufflers design of the mopar/borla vs a di do single muffler. The h pipe is supposed to provide balance between the two banks, albeit I don't think it scavenges as well as the x pipe. I do have some wicked exhaust velocity already comming out my exhaust tips with this set-up, so I don't think it would be that much of a difference to change out the h-pipe in the mopar/borla for an x pipe.
I think the reason why they went with an h pipe instead of an x pipe with the mopar borla is because the two exhaust banks arent equal length at that point, the drivers side has a little further piping cause it comes from the drivers side all the way to the passengers side. This is where the h-pipe comes in handy in balancing the two banks. IMO for the x pipe to work properly it has to be a true X set up and equal length piping going into the x pipe, meaning the entire exhaust set up looks like a big X and the actuall x-pipe would be in the middle of the truck. Main thing is the piping be equal length before going into the X-pipe. Just my $.02