It's also an unrealistic argument. Meaning I don't think people very often think through anything but the most basic level of the idea. It's not like the company is full of contract workers who just perform one task for a paycheck and then hope for another task so they can get a second paycheck.
These are largely salaried employees who are there. Sometimes things at work are slower or faster in your department depending on the workload.
If department A has a heavy workload but department B has a light workload, then you don't take employees from B and move them to A with the expectation that they'll suddenly be good at a task they're not trained at. Even if both departments have a heavy workload, department A getting done with something you don't happen to care about has no bearing on how long it takes department B to finish their workload.
