The CallActivity property on an object determines if the object will have its CustomActivity (custom code) and Activity (generated code) methods called. This value defaults to true so that all Objects are fully-functional; however, this can be set to false if Activity calls are not needed.
Setting CallActivity to false can provide performance boosts even if the CustomActivity is empty as actual method calls are slower than the contents of the actual methods – especially when dealing with virtual methods (Activity is a virtual method).
CallsActivity and PositionedObjectLists
PositionedObjectLists which are contained in Screens and Entities will call Activity on all contained instances. Setting CallActivity to false will disable this functionality.