No, you are not missing anything. Making the parameter final has no effect on anything but the method body. Generally I don't bother with setting variables final except in setters or constructors (i.e. when the parameter and a member could be confused) but I guess if you are paranoid it makes sense to always do it.
Regardless, Java is always pass by value so the author's comment is very odd. I'm actually quite concerned by it. Any intermediate Java developer knows there's no 'out parameters' in Java. At least not directly.