Why on earth would the designer of a 40k game leave out detailed info on Chaos adversaries, Tau adversaires (there isn't even kroot or vespid in the book), never mind Orks or Eldar? That suggests a prospective player looking at DW and thinking "wouldn't it be cool to have a Kill Team infiltrate a Chaos stronghold to retrieve something while being shadowed by an inscrutable and possibly dangerous Eldar squad after the same item" is asking for something beyond what a 40k Space Marine rpg offers with the implication that such an idea is thus not in keeping with the setting. How does that make sense? Ok he can wing it, or create his own stats, but that's not the point.
A game should give the players all the tools they need to play the kind of adventures reasonably expected within the setting. That isn't the same at all as asking for EVERY creature/entity to be statted up either. It is completely contradictory to say, on one hand, here are the rules for playing space marines and kicking ass, then on the other 'do it all yourself'.