I have no idea what google maps does.
if I plan a route from Amsterdam to Paris to Milano and "export" it from Google maps to routeconverter I only get the route to Paris.
Some time ago I wrote my own webpage using google maps DHTML and javascript stuff and also using large parts of christians Javascript stuff.
When I plan the same route (Amsterdam->Paris->Milano) and export it to kml file (via copy&paste into text file; so no link copying here) and open that kml in routeconverter, the complete route is correct.
So, routeconverter does it correctly if it gets the correct data, and the "&output=kml" option from Google Maps is not correct.
You can try yourself with my webpage:
http://harryvanderwolf.dyndns.org/gmwc/
Just add the destination in the top line and press go, add the next destination and press go, ..., press the "Calculate Route" button, and export to kml (via copy into text file and save as kml; Hey, it works. It's not the most luxurious routeplanner in the world).
I stopped working on it after Christian improved the osx version of routeconverter and (the pre-release version of) routeconverter now seems "complete" for OSX.