Sometimes they don't know what they hired you for. As in have no idea how the task should be done and how much time it can possibly take. That can be unethical.

Sometimes they don't know what they hired you for. As in have no idea how the task should be done and how much time it can possibly take. That can be unethical. If you have spiky workload and work on fun projects or just learn, I believe that to be fine.