Didn't he also do his active duty as a USNR officer? I don't think he ever was actually a USN officer. (I was enlisted so I'm not fully up on the technicalities of the distinctions.)
Sorry, I have exhausted my knowledge on this subject.
A reserve officer is a USN officer. All or virtually all, depending on the dates, ROTC graduates, and Officer Training School (name varies with time and by service) graduates receive reserve commissions. Only Academy grads get regular commissions as a matter of course. Then sometime after one makes 0-3 (Lt. in Navy and CG, Captain in the other services) one "meets" a regular commission board, if one is on extended active duty, which is different than active duty for training or temporary active duty. If the officer passes that board, then the are offered a regular commission. Reserve officers are first to be RIFed if and when a RIF occurs, and they are less likely to get the career enhancing assignments. Reserve officers who had served as enlisted members may choose to serve in their highest enlisted rank until eligible for retirement, as which point they can choose to retire in the highest rank held.