They don't refresh the ranges every two weeks, but when a product line is new they are often amongst the first to get new chips in. To be honest, if a Macbook Air CPU has enough grunt for office apps then I'm not seeing the issue at all. It's a cheapish all in one system with a good display on it and decent build quality.
You could probably swap my work laptop out for something with the equivalent beans of an iPad Air and I wouldn't notice. It's literally a tool to remote into other systems and look at web pages.
But how many people run office apps/programs on OSX?
The only place I could really see this being useful is as a cheap machine in receptions of design office, where having a Mac is important for image but where they use office apps alone. It may persuade some people to buy for personal use as well but those spending £900 must be a pretty small sector!