The NM flash suppressor is not 'more accurate' than an unmodified flash suppressor. The original reason for reaming them was supposedly because rain drops accumulating on the tines could actually deflect the bullet. Since it normally rains like a cow pissing on a flat rock off a 40-foot cliff during the national championships at Camp Perry, OH, this is a valid concern.
A properly modified flash suppressor is actually modified in four separate dimensions, rather than merely having the tines reamed out.