Florida schools require students to take a certain number of credits in the summer. I’m guessing the 11 month contract is a way to keep the dorms full and to encourage students to take those required credits their first summer and not put it off.
If you live at any school off campus, you’re likely going to pay for a 12 month lease. My daughter did, twice, and didn’t live in the house at all in June or July, and only for a week in May. The lease price was similar to 8 months in the dorm.