Quite amusing ..... It is to be hoped that the Italian Navy who wanted Harriers instead of the EH-101 were aware of the technical differences....
.... All three engines are connected into the main transmission....The third engine is not always on line and is normally only used when required.
Nothing different or really new there then.... even in the recent past the Tridair conversion of the Bell 206L used the 'switch-off' option to make up for the failure to enlarge the fuel tank. So not an option to be scoffed at in itself.