It isn't a true automatic installer
It is. The web page it takes you to is to load the latest .NET framework on your desktop/laptop so that the installer can run. Everything you need for the PPC *is* contained in the installer.
Another way of getting the latest .NET, instead of trying to pick the right one from the page presented, is to use "Windows Update"
http://windowsupdate.microsoft.com/ as that will present you with the correct one for your system.
Cheers,
Eddie