I feel people who benefit from this "diffuse state" are those who already have a base level of competence in their field or challenging problems they're trying to solve, and so boredom gives their brain an opportunity to express creativity in that domain.
For me, my brain is just "quiet" when bored. It doesn't come up with "novel ways to solve problem X", or "a brand new idea". When it is at all noisy, it is mostly regurgitation of thoughts I've already had before, replays of conversations from the past week, mundane things like that.
Does anyone else feel this way, or is it just me?