Half the gust factor only works for lighter winds and long runways. Example, my Cessna approach speed is 70kts. Today wind is 18kts G30, half of gust factor is 6kts giving an approach speed of 76kts. Enter ground effect wind is in the ebb after a gust and you are way to fast.
It is much better to fly the correct numbers in the correct manner.
But hey what would I know.