The standard flight-level reduction rules don't apply with this storm, based upon surface wind measurements from a multitude of sources. This is not uncommon for storms in the mid-latitudes, storms that have been disrupted by land, storms feeling the effects of upwelling and/or dry air, or storms in their organization phases. Flight level winds at 700mb of 72kt which may normally correspond to that 74.52mph figure (90% reduction) are likely lower, probably necessitating an 80-85% reduction factor based upon the aformentioned surface measurements. Simply put, when you have actual surface measurements, you almost always want to go with those over estimated fields from upper-levels, as no two storms are alike.