I've worked on (unrelated to nuclear stuff) computer simulation projects for the Navy where they had standard, notional models of the battleship which had the same sort of general properties you'd expect a battleship to have, but wasn't based on the design of any real battleship, so they could share them with researchers to develop their codes on without having to worry about revealing classified details.

Wonder if this isn't something similar, if the DoE has some sort of "standardized notional warhead" design they can use to give to outside researchers without having to give every post-doc and grad-student a security clearance.