DOJ doesn't make "rules" when it comes to public law. They enterpret and enforce but they don't make law. They have to stay within the same parameters as everyone else.
The source is me. I've been selling knives and guns in CA for almost ten years and I'm pretty familiar with the pertinent sections of the CA penal code.
PC12020A identifies and defines folding knives and dirks or daggers but doesn't limit the blade length of either type. It limits the blade length of belt buckle knives (like the Bowen) to 2 1/2" and that's about it.
It prohibits dirks and daggers from concealed carry but doesn't restrict the possession or open carry of such knives. (Single edge or double edge, it doesn't matter.) It also prohibits the possession, sale or carry of several knives that look like something else such as writing pens or tire guages or lipsticks, etc.
653K (the switchblade statute) defines switchblades and limits their blade length to under 2". It also prohibits the sale or transfer of those with longer blades to ANYONE. (LE, military, EMT, etc. are NOT exempt from this under CA law.)
The education code limits the length of a folding blade carried into a public building (courthouse, schoolhouse, etc.) to under 4". The reality there is that practically any sharp object has been banned from almost all of these buildings by local policy.
I had to visit the the local Social Security Office awhile back. They even had an armed guard in there. She made me take my large Sebenza out to the car. I guess they figure all us geezers might sudedenly become terrorists and take the place hostage or something. (After trying to do business with that bunch, maybe they have a point.)
As I said earlier, some cities may have ordnances that restrict or limit what someone can carry but the state doesn't have much in that area.