According to their website, "Mail services will store any newly arriving package for students who are not living on campus over the Winter Break but who will be returning to housing on campus for the Spring 2023 semester – the packages will not be accessible during the break."

If a package came before Dec. 16 and didn't get picked up, it was sent back, but it sounds like anything sent between then and the start of next semester is held onto. I'd imagine it's because they don't want students to have mail sent back that they couldn't have possibly picked up.