well the default sort order of categories is ASC not DESC meaning they are sorted by their id field. You manually set an order in Admin => Edit Categories.
Default sort order in the edit category screen pertains to the photos not the categories themselves.
There is no explicit way to always place a category at the top of the list since all we can do is grab the last sort of any subcategory and increment to the next one which is what we do.
So if you have 7 subcats we check to see that number and go to the next one. To sort a subcat always on top that means you need to sort every last subcat again which is not done.
After you create a new category you need to set your category display order again.