SelectionStampInBIFFExport=1 DOES print your selections in your Excel when the qvw is hosted in the QlikView Server.
I'm not too sure about that document you refer to in the resource library. It tells you to edit the ini file and then restart the QlikView Server but you will not be able to save the ini file if the QlikView Server service is running as it locks the file.
The document also says to add the entry AllowSessionCollaboration=1. This option should be modified using QMC not by editing the ini file and anyways it has nothing to do with the Excel exports.
The doc also says to put the excel entry below the entry for AuthenticationLevel=2 we don't have that setting in our ini file but there is a section labelled [Authentication] but your Excel setting should not be in that section it should be in the [Settings 7] section.
I would advise you check you ini file again to make sure your changes took place and that the ini file wasn't locked and that they were in the right place. Shut QlikView Server down first, restart after the edit.