He's very efficient with prose and I find it a joy to read (well, given what he's writing about it's not always joy, but still). I'm not sure he's following that rule 100% of the time, but it's close. Depending on the setting, you can often describe it through characters' actions or how it shapes them.

> Is there no room for describing the setting? Is there no room for mood?

You mean the character of a place?

The “mood” should reflect the character not the author’s desire to detail out the room.

Setting would provide the context for action or characterisation to occur in a meaningful way, or provoke it, so it is necessary part of both (if done for either of those purposes). Given that, the charitable interpretation would be to only provide enough description of the setting for that.