It's funny, because in order to become SF you need to enlist (or commission) go through regular training, then pass selections. All of which would appear in your military record.
And if you do write a book about declassified ops some of the info is still classified and can't be used. And if the ops are in fact sensitive and still classified you can go to jail.
Hence Richard Marcinko's biography (the real one, not his rogue warrior series) he actually did time for publishing information about the creation of seal team six and the miss hap at fort knox.
And that was just "training" missions he got arrested for.
edit: And i know some SF soldiers and retired SF soldiers, their rank and military file can be accessed through AKO and you can see that yes in fact they enlisted in the army. IT wont tell you about missions they have done, but their record is there. So the fact that he removed his rank and changed the story to fiction leads me to believe his lawyers informed him that he could be sent to jail for impersonating a soldier.