This sample demonstrates the defer layout update feature of the pivot table. The defer layout update allows users to refresh the pivot table on-demand instead of during every UI interaction.
Deferring a layout update can be useful when you need to remove or add multiple fields in a report and you don't want to update the pivot table after each change. Now, you can update a pivot table after performing all changes at the report level in the field list resulting in better performance.
In this sample, the Defer Layout Update option can be enabled or disabled via field list UI.
In general, this feature can be enabled by setting allowDeferLayoutUpdate as true.
More information on the defer layout update can be found in this documentation section.