For a method with @SOAPBinding(parameterStyle=SOAPBinding.ParameterStyle.BARE), the JAX-WS RI generates WSDL with a global element name and message part name that are the same as the operation name. Tuscany generates WSDL with a global element name and message part name of arg0, and it adds soapAction to provide the operation name.
The JAX-WS specification says that the global element name and message part name must be the same as the operation name, so Tuscany is generating WSDL for bare operations that doesn't conform to the JAX-WS rules. The JAX-WS specification also says that soapAction should be null unless @WebMethod(action=....) is specified. The Tuscany WSDL generator should use the correct JAX-WS mapping for the global element name and message part name, and should remove the nonstandard addition of soapAction.