Clarification on JavaDoc Writer::append(CharSequence)

[Markus KARG]

Dear Core-Lib Devs,

the JavaDocs of Writer::append(CharSequence) literally says:

      * <p> An invocation of this method of the form {@code out.append(csq)}
      * when {@code csq} is not {@code null}, behaves in exactly the 
same way
      * as the invocation
      *
      * {@snippet lang=java :
      *     out.write(csq.toString())
      * }
      * ...

I am kindly asking for an authoritative clarification how this is to be 
understood:

* (A) ONLY the particular implementation found in Writer.java MUST 
invoke "csq.toString"?

* (B) OpenJDK's OWN subclasses of Writer MUST invoke "csq.toString"?

* (C) ALL subclasses of Writer (even third-party code) MUST invoke 
"csq.toString"?

* (D) ...?...

Regards

-Markus Karg