module naming syntax

I'm puzzled about which utility should be more flexible about the module 
naming convention.  With Java 11 from OpenJDK, I notice that

     java --module-path=jaxb-ri/mod -m 
com.sun.tools.xjc/com.sun.tools.xjc.XJCFacade -d out -p generated 
Schema_Specification.xsd

works as desired, but

     java --module-path=jaxb-ri/mod -m 
com.sun.tools.xjc\com.sun.tools.xjc.XJCFacade -d out -p 
generated.armisxml Schema_Specification.xsd

does not (only difference is the use of '\' and '/' in the module name).

When one tries to use a Java task in 'ant', it translates the forward 
slash to a backward slash, e.g.,

   <java fork="true" modulepath="axb-ri/mod" 
module="com.sun.tools.xjc/com.sun.tools.xjc.XJCFacade">
                 <arg value="-d out"/>
                 <arg value="-p generated"/>
                 <arg value="Schema_Specification.xsd"/>
  </java>

Running 'ant' in verbose mode, it shows that the argument "-m 
com.sun.tools.xjc\com.sun.tools.xjc.XJCFacade" is passed to the Java 
program.

So, which program should be more flexible?  I haven't found a 
specification of what the module name specification should be. But the 
OpenJDK Java program requires that a forward slash be used.  Should 
'ant' not translate the forward slash into a backslash?  Or should the 
OpenJDK Java program accept either one?