It was true for Formativ Client 1.0 but this option is now valid for Formativ Runtime 1.5 because of the new availability of the Business Solutions Pack 30-day trial and the other free solutions which ship with the product (No Junk Mail, Today View etc.).
Unfortunately it appears that this restriction was erroneously left in the documentation and we will update it.
We tested the config file again and the parameter following your message and it worked in our case. One thing to be aware of is that, if you are not using ‘Silent’ mode, during the installation you will still see the options checked for the applet solutions regardless of your configuration file settings. However, if you proceed, the applets and data will not be installed. When designed, it was anticipated that the configuration file would be used in silent mode (no user intervention) and thus the user option dialogs would not be seen.
Are you going through the full installation cycle and still not having any success?