Unexpected output from `java -Djava.security.debug=help`

The security guide contains this advice around use of the security debug property:

==
To see a list of all debugging options, use the help setting:
java -Djava.security.debug=help
==

That option doesn't seem to work since JDK 10. Instead we get the standard java usage help message...

$ ~/jdk/jdk-10/bin/java -Djava.security.debug=help
Usage: java [options] <mainclass> [args...]
           (to execute a class)
   or java [options] -jar <jarfile> [args...]
           (to execute a jar file)
   or java [options] -m <module>[/<mainclass>] [args...]
       java [options] --module <module>[/<mainclass>] [args...]
           (to execute the main class in a module)
.....