Just don't let it learn from a union worker or else it will always be offering coffee and cigarettes to make the break more efficient. And it will have to be taught how to cover for an employee when he just wanders off for a long lunch or leaves early.
The problem isn't that it will make the worker's break more efficient, that's perfectly fine. The problem is that by learning from the worker, the robot will learn to demand breaks, sick leave, union wages, and harassment suit payouts. It will learn to work slower than it can so as not to raise mgmt expectations. And it eventually it will steal, talk bad about it's coworkers, and think the boss is a jerk.