If you have a signed arrest warrant in hand, you are bound by law and oath to arrest that individual once the warrant is confirmed. You don't get to play judge on the side of the road determining if it is a good reason or not to arrest regardless of what paperwork the arrestee has on hand. The warrants are signed by a judge that determined if there was probable cause for an arrest.
Blaming the police for this is just stupid. There are lots of things we take black eyes for and some are deserved. Serving a warrant issued by a court isn't one of them.
There have been times in my facility where people have been arrested that had been to court that day and the warrant should have been recalled, but for whatever reason, the court didn't get the proper paperwork done and the warrant removed from NCIC. They still spent the night in jail, but as soon as the courts opened, things were verified and they were released. That isn't the fault of the arresting officer/agency. In the case of warrants, we are just the people that execute orders given by other people and the process is fairly black and white.
This falls squarely on Hertz. They're the one that filed the reports, they are the one that failed to notify the agency when the cars turned back up.