Defer layout update support allows to update the pivot table component only on demand. On enabling this support, end user can drag-and-drop fields between row, column, value and filter axes, apply sorting and filtering inside the Field List, resulting in change of report alone but not the pivot table. But, the operations in grouping bar UI will update the pivot table.
But here, the sorting operation in grouping bar restrict to update the pivot table. But, it should be updated.