Didn't the US Army have its own journalists? (Al Gore?)
It doesn't seem crazy (but it may be wrong) that he gor some course credit for whatever training the Army might have given him, and the actual journalism he might have done.
(Seems to be something within the Signal Corps, these days.)
Of course, that assumes that the people doing training and assessment and posting didn't have an overriding need for something else. But it's also a military niche that could put him in a lot of different places, from downtown Saigon watching a VC being summarily executed to a Huey, full of AirCav, trying to stop somebody bleeding out in his lap.
That's the theory, that you can get credit for training in the service. Theoretically, the training I got in the Army was worth 2 years of college, but somehow I could never convince a school to believe that. Things may be different now ...
As for what Sol did in the service, the jobs I can think of that would give him the most chance to move around, are journalist, criminal investigator, courier, counter-intelligence operative, or clerk to an Adjutant General's investigative or trial team.