What Class is calling the spawning of the SMA?
When you drag a mesh in to the level the editor by default creates a static mesh actor and sets your dragged in mesh as a component.
No different that this
Static Mesh Actors are set to be Spatially Loaded.
When you package your UE5 project, all the data associated with your World Partition, including the spatially loaded actors and their associated cells, is included in the build. The engine then handles the loading and unloading of these elements at runtime based on the player’s location.