The "Do not display the 'Original Workbook' choice" option in XLS Padlock removes the possibility to load the original, unprotected workbook on the Welcome screen:

 

 

With this setting enabled, the welcome dialog will only offer the possibility to load an existing secure file. This option is particularly beneficial when custom save files are provided to end users at the outset, ensuring that only the secured versions of the workbook are accessible upon startup.