That does seem possible, so most likely I'm annoyed with the character's behavior and that sort of one-track mindedness more than anything. It just appears to be a very specific hypothesis and very much plausible, which didn't fit coming from a grunt. While I don't put 100% faith in the "specialists," it just seemed unlikely that a grunt would figure it out.
What evidence is there that the ship captain was former military? Unless they mentioned that somewhere, the guy could be a merchant marine, a ship captain who just floats from location to location. It's just as likely it was poor writing and you're reading too much into it.