MoveComponentTo is declared at UKismetSystemLibrary::MoveComponentTo.
The action is updated in FLatentActionManager::ProcessLatentActions, in FLatentActionManager::TickLatentActionForObject and finally in the virtual function UpdateOperation (in FPendingLatentAction).
Callback is called here: CallbackTarget->ProcessEvent(...); (in TickLatentActionForObject)
MoveComponentTo
The action struct is FInterpolateComponentToAction