Correct.  Electric motors are not usually used to adjust the stem positions in control vales.  Normally control valves are adjusted pneumatically.  The electronic signal is transmitted near the valve and is converted to proportional air pressure that is transmitted to the valve via a short pipe.  The pressure slightly deforms the diaphragm and changes the stem position.



For more details on control valves, refer to the Instrumentation section in the Educational Materials of this WEB site.