Ok, no one answer, so i will assume that, Asset has something like AssetDefaultObject (like ClassDefaultObject for UCLass), that AssetDefaultObject is loaded once and then used for instansing Actors of corresponding Asset.
Every Asset is an Object which has UClass with ClassDefaultObject, so (Asset loading) == (creating Object from Asset). Then created Asset Object is used as Component for existing Actor, or as archetype for creating new Actor.