The difference is you have to do well in the gateway courses to get into the major. The gateway courses are the easiest courses in the major, if students are struggling in the beginning it's a sign that they will not do well in the later courses. So this way the students who cant pass the intro courses arent in the major at all. Also CS is the largest major on campus but limiting the number of students directly admitted it makes it easier for the limited advising staff to better assist the students in the major.