Everyonce in a while I have issues with the {% %} macros. One thing I usually will try, which usually works is to use this syntax instead.
{% QueryString.GetValue("key") |(identity)GlobalAdministrator%}
If the issue isn't in the macro, then you may need to have a script running at the server level to set the sort property on the page load or the reload data method. Depends on what is in that webpart. You could also customize the webpart by cloning it and then you could have full control, which probably would be pretty easy, as you can get the querystring value and then set the property from there as well.
Not sure if that will work or not, but may be worth a try.