Should add that all branches of the armed forces go through that same exercise in Basic Training, but this particular view is of the marines. In the end the whole armed forces has the same set-up, so it's not a "marine basic training".
That's true, but, most units trains their recruits to join their regiment. And that's especially true at Amf1 and K3.
So yes, no such thing on paper, but everyone who's been there and seen them knows what's what