Template:Filename and Template:Filename allow you to execute commands at the beginning of the X user session, before the Window Manager is started. Therefore it cannot be used to start window-based applications. See Autostarting#Graphical for that.
Making it compatible with xinit
It is possible to make xprofiles compatible with these programs:
All of these execute, directly or indirectly, Template:Filename (usually copied from Template:Filename), or Template:Filename if it doesn't exist. That's why we have to source xprofiles from these files.