No this is not true. Oregon has preemption through judicial ruling, the Delgado case deals with knives, they had another case that dealt with switchblades a couple of years later.I forget the case.
You can open carry any knive or blade anywhere in the state. The state law dealing with public buildings lumps knives and all that fun stuff in with firearms. HOWEVER, if you have a CHL, you are exempt from the public building law (except courthouses and jails); therefore, you can open carry knives in these places with a CHL. Some cities may have knive laws no the books but the State Supreme Court was very clear on the subject. Open carry and possession is a right and laws to the contrary are null and void.
The CHL only applies to handguns, so unfortunately, you can not conceal knives with a CHL.