JRE create provide below output:

  -x, --extension <name> Select one or more optional components to be included in generated runtime.
                               To select more than one component, this option will accept a comma separated
                               list (with no spaces) as well as a single value. Valid values are: fx:graphics,
                               fx:controls, sunec, sunpkcs11, locales, charsets, nashorn. Note that selecting
                               fx:controls will also automatically include fx:graphics.

FX is out of scope for 8u60 so that it should not be mentioned in "Valid vaules" section