George, the jet HAS the ability to carry DTs. They haven't been tested and given a clearance. There's a huge difference. E.g if the pylons aren't wet-plumbed there is no ability to carry usable DTs. That is not the case here. As and when the Services pony up the money for test it's there.
You can guess if you wish but the average fuel improvement with DTs was around 9%. That wasn't worth it.