This is how I think about it, FWIW...
Final approach speed in gusty conditions = final approach speed as per POH + all the gust factor. The gust factor is the largest possible amount of airspeed you could lose due to a sudden gust; e.g., headwind component of any reported gusts.
Should the gust fail to materialize we will arrive at the flare with too much airspeed , resulting in a long float. However, provided the gust factor is less than the steady headwind (if that's not the case we need to watch out!), our groundspeed is still less than the calm wind groundspeed at the normal approach speed, so landing performance should not be a problem.
BUT: This requires using the actual POH figures corrected for current conditions, including reduction for weight lower than maximum. Can't take a "standard comfort figure" such as 70 kts in a 172S and add all the gust to it...
Making sense?