I'm still awaiting a reply from the forum 

When you import the jar into a codeset that is available at startup you do not need to explicitly add the jar to the class paths.  If you do not import the jar into the database and instead have it on the file system of all of your nodes you would need to update the paths to include those jars.   And also prior to 6.1 the majority of the code was in jars on the filesystem and not in the database so in those versions the classpaths were much more relevant.  Why you would want to do this in 6.x+ is perhaps because you are trying to make sure your jar file ends up earlier on the classpath. However, the order that the classes in the database and the classes on the filesystem get added to the classpath is non-deterministic so that isn't a good solution.  While it might work there is no guarantee that the next time that you start your system the order of the classes on the classpath are the same.