It's interesting to note, the CHP Motor Cops who I've had the good fortune to fall behind on the freeway do not follow this guideline. Even so, they are very highly trained riders and do have an obvious look that makes cages widen the gap on instinct. To increase visibility, I just ordered the Biker Buddy P+1 headlight modulator. It will help in that regard.
http://www.bikerbuddy.net/content/bikerbuddy%E2%84%A2-p1%C2%AE-headlight-modulator Just don't use it when riding in groups. It can be irritating having that in the rear view mirror for long periods of time.
I believe the speed limitation will be used for those who are doing crazy speeds through nearly stopped traffic, but not because someone passed between two cars safely, when given the room to do so, however traffic is flowing.
We split here in California quite a bit, but I try to be courteous, so not to upset those sensitive souls stuck in traffic. The heavier the traffic, the more contentious it can be. I've heard of cages getting tickets when deliberately closing the gap by moving over when they see the bike. One of my riding buddies told me there was a CHP behind him and when the cage moved over to block, the
blue lights came on.

It's good to see something in writing, but I believe it is as much for the cage drivers, so they know bikes are going to be passing between them and it is legal.