The user wants to change some Web Preference at a user group level, but neither Strategy Web GUI or Command Manager display any option to do so:

… [FOR (USER "username" | CURRENTUSER)] TO (ALLPROJECTS | PROJECT "project_name");
APPLY WEBPREFERENCES DEFAULTVALUES FOR USER "JeanSmith2" TO ALLPROJECTS;
This is working by design.
In order to change any of the Strategy Web preferences at the user group level, the administrator must design a “made to measure” solution like a procedure based on Strategy Command Manager.
Please review the Command Manager documentation, Including a script within a script: Procedures