The specifics of it are; that those who have or indeed are serving members of the Armed Forces will have a greater potential of meeting/dealing with or even being SF. Sadly, the majority of people espousing their knowledge on threads such as this get their info from "The man in the pub" who just happened to be the 18th man on the balcony that day. That or Wikipedia, which, to be fair, doesn't always get it right.
That's not to say all the ex/serving bods are right either, but they will have more insight into the subject matter at hand. Though I suspect some of them may just have been sat in a hangar, steam-cleaning vehicles etc after they returned from patrol.