Spinner CSS Classes

Spinner CSS Classes

The specs for spinner currently say:
The spinner's generated CSS classes should be as generalised as possible. A self standing spinner will use the ".ui-spinner-" namespace but if incorporated into a timepicker it should inherit the timepicker's namespace, e.g. ".ui-timepicker-".
This goes against our current standard that class names are not configurable.  Is there a reason this needs to occur as opposed to the timepicker just instantiating a spinner and then adding additional classes to it?  Is there a strong need to replace instead of append classes?