It is Tableau feature that you have already understood. Twbx file do not update with the updated data as it created its own data in Temp folder.
The tbwx file is like zip file. You can use programs like Python to unzip the tbwx file, open the tbw file and edit/replace the data connection. Perhaps you need a csv or excel file where you have information relating to your data file (so that python knows what data to replace).