"Because if you manage to finish the tasks early and leave at 2, they'll make sure you have enough tasks so that this doesn't happen again."

Yes. I've had managers get offended at the idea of taking a break when tasks are complete because you should be jumping on the next thing.

From what I've noticed, though, jumping on that next task doesn't help your career at Big Corp in any way and usually doesn't significantly lead to more personal accomplishment.

Taking some time to reflect can have a big impact on what you accomplish, though.