It's probably there on the Black but you can't see it in those pictures. I don't think it's a grill. Looks like a partially see-through section of glass that is covering a sensor.
The front facing cam occupies the location where said proximity sensor use to be. Seems like a reasonable place to put it since it mainly functions to turn off the screen backlight when holding the phone up to your ear on phone calls. But hey, this won't be useful anyway, because everyone will be using Facetime.