If I am running a hack and I use this, and the hack successfully runs the first copy of XSelect 0.9, I can know that the hack is successfully installed. If there are any problems after XSelect 0.9 is run, those can likely be far easier to fix just knowing that the hack was successfully installed and that XSelect 0.9 successfully ran.

On the other hand, if XSelect 0.9 fails to execute, then people can know it is either a problem with XSelect 0.9, or the problem results from the way the hack is installed/used.