The reason for above is unknown, although there are some possibilities of the following, 'since Emperor Chuai's death was not announced officially after he died, and it was temporary measure,' or 'there was no particular reason, the word Shosei was being used as a custom, since it also meant Regent after all,' or 'Shosei meant temporarily government since Emperor Ojin was officially considered as proper Emperor and he was called Emperor Taichu (Taichu means inside mother's womb).'
その理由は、「仲哀天皇がいまだ崩御していないという建前をとったためその代理だから」という意味か、または「特に理由はなく、称制も広義の摂政の中の一種という建前でただ慣習的に称制という言葉が使われなかっただけ」というわけなのか、あるいは「応神天皇は胎中天皇と称されたように胎児の頃からすでに正式な天皇であってその代理」という主旨なのか、いずれにしてもよくわからない。