My experience is courses come in one of 3 flavors (ie GE, major, and other). In a quarter system it would be the very rare student that would have to fill every quarter with nothing but GE and major reqs in order to graduate in timely manner. There will always be space to fill up one’s dance card with some “other” courses, or in case of a starting freshman, just take 3 courses of 4 units each just to get their bearings in his/her first quarter freshman year. The only problem is if the student is taking sequenced courses like bio, chem, but even then most students could work around starting with only 12 units (aka 3 courses) and still graduate in timely manner.