Those "properties" aren't properties of groot. See this documentation page for a description of that syntax for setting default property values for other Handle Graphics objects that will be created under groot in the future. Note that you can set the defaults at a more granular level too, setting the default for all Axes created in a figure without affecting Axes created in another figure as an example.
At least theoretically you can set the default property value for any settable property of a Handle Graphics this way. [I'm not aware of any exceptions.] Some may be more useful than others (setting the 'DefaultLineXData' at best won't do anything, and at worst could cause your attempt to create a line to issue a warning and not draw the line.)
