Does the code scanner scan the left code and only open the left door?

That's not true. Large code scanning cabinets are generally equipped with two scanning ports, in order to avoid queuing congestion when in use. There is no setting about which side of the door will be opened. Of course, it is not excluded that two cabinets are combined into one, and a code scanner is responsible for one cabinet. It's just that the connection is relatively close, and the splicing of the two cabinets is not obvious.