Not necessarily. Students can sign up for only Fall Clean up and/or only Spring Cleanup and/or only Post-Commencement. One does not have to participate all year. It’s flexibility is one of its selling points (I guess).
But one thing I have not seen on this thread is that Dorm Crew is not limited to just work study students, i.e., those with financial need. Any H undergrad can sign up to make a few bucks.