If it was his mothers intent on having him registered as an American it is completely plasible that his grandmother put the announcement in the paper with her address. Once he and his mother made it to the states all she had to do was apply for a delayed birth certificate. I think that is why he doesn’t want it shown. According to the article prior to 1971 it possible to give a Hawaiian citizenship even though the birth didn’t occur there.
Yes, granny could have applied to register his foreign birth with the state of Hawaii. That opportunity was available in Hawaii at the time. (According to the posted article, that same procedure would be abvailable even today for babies under one year old.)