Says who? ......... "most strongly representative". With a grass strip.
Forget, as you indicate, it was English Heritage!! RAF Bicester is almost pretty much the only station left anywhere that represents a station as built ie it didn't get developed further. Despite it only having grass runways the technical site is pretty much complete. Many stations were built with grass runways and later developed to add concrete runways. Therefore it can be described as "most strongly representative".