The second new rule is slightly more complicated to explain.
Under the new rule, a receiver will not be considered in motion and therefore will not be charged with a false start if he twitches one foot or raises it off the ground, as long as the other foot remains planted on the ground and he remains set for at least one second prior to the snap. By contrast, if all eleven players have been set for at least a second and a receiver moves both feet, he will be charged with a false start and assessed a five-yard penalty
Basically, it looks like the league wants to reduce the number of nonsensical false-start penalties triggered by motions that confer no advantage to the receiver, all the while making it more difficult for the receiver to gather any momentum prior to the snap. More's the pity. I had kind of hoped we might see a slight liberalization of the pre-snap motion rules to allow for something resembling the chaotic offensive formations we see in the CFL.