The suggestion that there isn't some powerpoint presentation that the US Navy created (or consultants to them) that says "if we invest $X millions/billions to create smaller fuel jet fuel tanks we won't save money" is total nonsense. That's not how capital intensive government projects work.
Couldn't edit my original but I finally had some time to google this:
> The U.S. Department of Defense (DoD) is the single-largest consumer of fuel in the world and Jet fuel accounts for 71% of the entire military’s petroleum consumption. Therefore, DoD needs to maintain a strong logistical support to provide jet fuel for its equipment across the world.
That doesn't mean that synthetic is a cost savings measure.
The DOD could be interested in it purely for the tactical and strategic advantage.
For example, it could cost 2X when everything is taken into account, but still be attractive because it provides a type of combat advantage that can not be obtained in any other way. Not everything is fungible.