It is unclear as to when the kogo-ishi were built, and even if they are of the same era it is probable that we only collectively refer to the wide variety of constructions as 'kogo-ishi' based on the distorting prism of what remains today.
現在まで、神籠石が何時頃作られたかも判明しておらず、成立年代は同じであったとしても、これほど様々に状況の違うものを現在的視点から神籠石と総称している可能性は高い。