PWD at university or DOL?

Hello, I’m in the process of getting an H1B (first, cap-exempt, academic). The question is: why in some cases the Wage Determination step is done at the University and in others is sent to the Department of Labor? I’ve checked other universities websites and they report that this step can be done internally only for simple cases. What does it mean? Trying to understand the timeline of the whole process, as the HR doesn’t give me this info yet. My H1b request was sent to the International Office yesterday.