I am not a lawyer, but I disagree. The wording of the statute entitles (requires?) "[t]he spouse of the person renting the vehicle, if the spouse is a licensed driver and meets any minimum age requirements contained in the rental agreement" to be considered an "Authorized driver." State law supersedes Hertz's terms and conditions. There is no need for a spouse to be explicitly added on to a rental agreement, since said spouse is already automatically authorized to drive by state law. Hertz appears to be in violation of Oregon statute.

That said, someone knowledgeable about state statute should never even need to ask the Hertz counter sales staff if the spouse must be added on to the contract. Even though the OP's spouse is entitled to drive, the act of explicitly adding someone on may entitle Hertz to charge for that service, even though it is unnecessary and duplicative. That mirrors an experience I had years ago at a Hertz counter where I asked about adding a coworker on; the Hertz agent told me that if the person was a coworker, they were automatically authorized to drive, but if I were to explicitly list them on the contract, the system would trigger an additional driver fee that he could not waive, and so there was no reason to add the coworker on as they were already entitled to drive per the terms of the contract without adding them on by name.