I had a CDL-A a long time ago, that was the rule then. Big shops made sure you stuck to it (or so they said) but I also did here that they will indirectly force drivers to drive a lot more than that. When you hear about truckers making six figures, that isn't from 8hr days for sure. They even gave you a tip during training: if you open your truck's door, you're losing money. What happens when they force you is you don't get the trips you want or that are lucrative if you have a reputation of doing bare minimum.