DefaultMarshaller.java does not use the supplied ObjectMarshallingStrategy as far as I can tell.
When you create a Marshaller like this:
And then use it like this (or similar):
...the supplied strategy's read() and write() methods are never called.
This is because DefaultMarshaller.java line 132 does not use the DefaultMarshaller's strategy, but the strategy of the incoming StatefulKnowledgeSession instead.