There is important aspect to the Front Panel defer updates nodes, this is from the help
When you set this property to TRUE, LabVIEW redraws any front panel objects with pending changes then defers all new requests for front panel updates. For example, controls and indicators do not redraw when you change their properties or values. If the operating system requests a redraw, such as if the window is no longer behind another window, LabVIEW redraws the front panel with the current properties instead of the original properties. If FALSE, LabVIEW immediately redraws the changed elements of the front panel.
So when you use it, it actually causes the front panel to redraw twice.