It strikes me as being something put in place for things to come. Just like they leave all the Public Beta resources in there, I would assume the new addition of the mini toolbar is for something on the horizon for the OS. The Extras.rsrc is becoming a wasteland for arbitrary elements. Thats why I look forward to resource switching changers, so I can strip all of the useless PB resources out of my theme files; if not for anything else, just so I dont have to scroll through the damn things when developing.