It's not their top priority at the moment. They'll probably sell a few hundred thousand of these whether or not Ars Technica or the Verge like this one or not. It's a niche product for Apple, but they committed to the MacBook and they know Intel's road map better than most. There will be an improved MacBook when Skylake comes out, regardless of how slow this one is. It's no secret that the Core M is no speed demon. Would I like a review? Of course, but I'm not surprised they didn't send out review unit, or more likely placed a later embargo release date (we might see reviews on the 10th).
The Watch is a huge undertaking involving massive research and development, as well as marketing. It's the first completely new product in the post-Jobs era. A thinner and lighter MacBook is an evolution of an existing product line.