the change is a WR can't come inside and block a LB low...period...even if it is a north/south block
•Wide receivers more than seven yards from the center at the snap of the ball 
can block below the waist only against
 a player facing him  or toward the nearest sideline.
•Running backs/receivers in the backfield and outside the tackle box (the area five yards on either side of the center) or players in motion can block below the waist 
only on players facing them or toward the nearest sideline.
Do the highlighted terms indicate North/South?  Maybe what we need now is a definition of a "player facing him".  Perhaps the WR runs toward the original position of the ball at a 45 degree angle blocks below the waist against the Linebacker who was "facing him" at the same 45 degree angle.