These shrines were under the control of Jingikan, a governmental institution in charge of Shinto affairs, and categorized as "Kanpei-sha" (Shrines served by Jingikan), and therefore, it can be thought that Jingikan had established the rule to pronounce the letter 良 as "naga."
これらの神社は、明治維新後、官幣社に列せられ、政府機関である神祇官の管理の下に置かれており、神祇官は、当時の研究水準を踏まえて「良」を「なが」と読むことで統一していたものと考えられる。