Are the two screws on the arbor washer required? Do I have to use European saw blades with the additional holes?

Because the European safety regulations require the additional securing points for saw blades, our saws have this feature and our German made Leitz Destroyer blades have the holes on either side of the arbor cutout to allow the pins in the arbor washer to seat into the arbor flange. 

Harvey table saws and blades come with this design due to the safety advantages they bring when the blade is spinning, but if you wish to remove the two screws in the arbor washer to use USA saw blades that do not have the holes cut out, this is considered acceptable by USA safety regulations and standards.