The directional stability could be affected when there is a short-term change in crosswind (while the aircraft momentarily maintains its orientation in space) and thus an angle of attack on the fin - if that gust (lets say 5 knots delta) remains constant, the resultant angle of attack is less for a higher TAS. Thats at least what I meant further up. Naturally, said stability will cause the airplane to decrab (if the new x-wind remains).