No inside knowledge here, but by framing with the viewfinder they mean PDAF (as opposed to CDAF). And yes tracking of a subject in motion. Works equally for shutter half-pressers as it does for AF-ON folk.
Wait'll we get on sensor PDAF (phase detect autofocus), then we can frame with the rear screen and still get PDAF, whereas currently we only get Contrast Detect Autofocus in LiveView. Of course the Nikon 1 series can do this today. Can't wait for them to scale it up to our DSLRs too.