Date Columns with Auto-Width set (in folder formats) don't respect the preference: 'show day names in date columns if date is within one week'. The column widths are calculated for the numerical dates whether or not that option is checked resulting in extra space in the column. Note the left file display's Modified Column width (with and without the option checked it's the same).
Not a bug. The date and time columns auto-size to ensure there's enough room for any date or time, by design.