If you duplicate the unapplied layrComp, then it is duplicated and a checkmark is displayed that it is applied.
In fact, this is not always true.
Checking is very simple. Turn off all layers. Create a new layerComp. Turn on all layers. layerComp will become unapplied. Duplicate layerComp using the context menu. The new layerComp will be marked as applied. But this is not true. All layers are turned on.