Why issuing "runstats" on a nickmane just update the statistics on the datasources and not on the federated server?
To issue a runstats statement against a nickname you need one of the following authorities/privileges on the table that the nickname points to:
CONTROL privilege on the table
But to have the statistics updated on the federated server for the nickname you need one of the above authorities/privileges on the nickname too. Otherwise if you do not have authorities/privileges on the federated database you will have updated statistics only on the data sources and not on the federated database.
Grant one of the above authorities/privileges to the user/group/role on the federated server.