Countries / Companies have several ways, standards and traditions, to report data in week, month, quarter and year.
For someone, calendar month and quarter is good.
For someone, they report by 4-4-5 quarters (4 weeks in the first month, 4 weeks in second and 5 weeks in the third). Typically every quarter will have 13 weeks. An year is not exactly 52 weeks, to compensate this you have a 14 week quarter once in every 5 or 6 years. Once you configure data by weeks, reporting it by calendar month needs additional effort. 4-4-5 fiscal month and calendar (Gregorian) month is not same.
General week is simply weeks without rolling upto quarters and months. You can map the general week to a custom quarter as defined by business. Only in general week, you have a model calendar that is less than a year. In all other options, you can add time to your model calendar in multiple of years only.
Based on requirements, the solution architect has to evaluate and choose the right setting for the model.