The "hidden" option is not working for this gadget. It appears on Special:Preferences#mw-prefsection-gadgets even after I hide it. Indeed, the loop which adds a preference for each gadget doesn't check for its hidden property before adding it to Special:Preferences (BTW: it also doesn't check if the user has the appropriate rights).
Topic on Talk:ResourceLoader/Version 2 Design Specification
The infrastructure is as good as ready and in place in the Gadgets 2.0 branch. It may not be used everywhere yet, we're working on it.
Thanks for the report (bugzilla:39025)