If the pay rate is the same, the expectations are the same. The hardest working teamster I ever had the pleasure to work with worked circles around the youngsters. His son was a hustler too. It was in their makeup.
You believe managers would abuse any power given to them, yet seem to believe that the slugs aren't abusing the power the vague contract provides.
Some routes are going to have a whole lot less stops per hour, bills per hour, tonnage, whatever metric a bean counter wants to assign to measuring the productivity of a given route. Same with breakouts, some are just going to take a whole lot more time than others. Given enough data, you can throw out the outliers and create a reasonable average. If the average can't be met more often than not there needs to exist tools for discipline.