AviatOR,
As you suspected, your friend is slightly misinformed. The F/A-18 has conventional rudder pedals and all the flight controls are fly-by-wire, mechanical backup only to the differential stabilators in the very rare case of a complete loss of electrical power. Multiple backups in the flight control system and 2 flight control computers. The computers do play a large role in output (i.e. rudder movement) in relation to rudder pedal input. If the pilot puts in full right rudder for example, the system will take into account airspeed, density altitude, angle of attack, yaw rate, etc. as well as other factors and will determine whether rudder or a combination of rudder, differential stabilators, ailerons and/or differential leading/trailing edge flaps is more appropriate for the aircraft's current location w/in the flight envelope. By the same token, left/right aileron input (with no rudder pedal input) may produce rudder movement because the flight control system essentially "knows what you're asking for" and will automatically give you optimum performance. A rolling-surface-to-rudder-interconnect (RSRI) helps to aid in preventing adverse yaw esp. at high speed.
Because of the fly-by-wire, the F/A-18 pilot rarely uses the rudder pedals much except for slow-speed, high angle of attack combat maneuvering where more rudder movement is available and is more effective at preventing nose slice off to one side or the other. Also obviously used in the landing configuration as required.