One question... why would a garden variety lieutenant on a swift boat have a top secret clearance? Is that standard? If so, it would seem there are entirely too many people with top secret clearances i.e. access to the most important secrets of the country.
Probably due to his position as a swift boat commander, and the possibility (however remote) that his swift boat could be sent on a TS mission
I was in the Signal Corps, 1966-67, I had a Top Secret Clearance, (required).... they did check. It was noted that I had received a speeding ticket in Newark, DE. I didn't put it on the clearance form.
One day when I was in the Army I learned that I had a secret clearance. I didn't even know about it. I was fascinated when the Battalion clerk opened up a book which had the war mission of my unit laid out.
I was just an E-4 anxious to get out because I was short, but I did have to do special duty which was really no big deal.
That was long ago and my unit has pretty much been disbanded and we no longer have the other units that were in place back then 25 years ago.