I believe this is on purpose. On dynamic views like, lists that update when the store data changes, you probably don't want the loading mask to appear each time the store updates.
Though I must admit that I did not find any methods that called this private method.
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I agree that you don't want to see the loading mask on every item change. But to the best of my understanding updateStore() is used to change the entire store, in which case the mask should be displayed and the events should fire.