I was also selected to receive an award by the ONR, however my current work and research statement were aligned with ONR objectives. One of the hurdles to overcome with the NDSEG (as I see it) is to show that your graduate school goals are aligned with objectives of a particular branch of DoD, rather than say the NSF fellowship, which is application agnostic. So, I don't believe the NDSEG just "divides up our applications". I believe each branch has overlapping yet different goals which are reflected in the applicant pool.