If I were to guess, it's because that there are a bunch of temps doing data entry. They get paid a bonus based on what percentage of data they enter. Then comes this one guy, and he starts getting 90% of the bonus, thus effectively cutting out the bonus money for the rest of the employees (in a manner someone may see as cheating the system)

That's just the other viewpoint of the story. Not saying it's most efficient, or right, but I can see a manager thinking that way.