Hi Ying Chow, welcome back and nice to see you again!
Good question. Facebook Importer uses the same import permissions that WordPress offers for importing content — which, you noted, is set to Administrator.
It might be possible to change that using a third-party plugin like User Role Editor to change those permissions, but otherwise, I’m afraid it would require custom development to accomplish. In fact, I just installed the plugin and checked it out and it appears there is an “import” option to grant permissions to other user roles, so that looks promising.
Cheers!
Geoff