For the previous post about NYU, I also received acceptance e-mail from the adcom professors. The letter goes "We would happily initiate the process of formally making a fellowship offer, but if you are currently holding offers from other institutions that you clearly prefer over NYU, it would be great if you could let us know". Similarly, I received an e-mail from U Penn, but it is not as explicit as NYU. It told me to notify them ASAP if I have a dominating offer.