The speedometer, which in turn, drives the odometer, is NEVER connected to the wheels. It is connected to the GearBox. Thus, driving in Reverse does not reduce the odometer readings.
To prevent tampering, there is a seal on the cable, which when broken/missing, some manufacturers void the warranty [Unless it is done by the dealer, and recorded, of course

] This was done because some mechanics used to attach a drill to the speedometer cable and
Voila! you had a
car belonging to the proverbial old lady who used it on sundays for going to the church.
Manufacturers use the odometer reading primarily for the warranty purposes [mostly of the drivetrain components.
Interestingly, LEXUS also stores the actual time the engine is in operation, so that it knows the actual usage of the engine [including idling].