Putting aside any conspiracy theories about "what are they hiding?" it almost certainly means the game is coming out hot. If they need every last second to finish up the game, to the point that they can't even let reviewers play a week before the game comes out, there's almost certain to be a huge day one patch fixing massive bugs. It's also pretty much guaranteed that there will be several bugs that they can't fix in time.
Probably a good idea to wait on the game and see the state it's in at launch, and whether they continue to patch issues after release. Though I suppose with the way the game industry is these days, this should be standard practice.