Kernal of truth is not truth absolute, as you pointed out.
“...why the Hawaiians did not practice cannibalism, when so many Polynesian groups did.”
You have the makings of a part-to-whole fallacy here.
Just because some Polynesian tribes practiced cannibalism doesn’t mean all Polynesian tribes engaged in this practice. We do know that the Polynesians practiced human sacrifice. As a matter of fact, my uncle once told me, in a matter of fact sort of way, that if the Ali’i chose your child to be sacrificed to one of the “Gods”, you felt honored that your baby was chosen. I was in my teens at the time, so I did not want to disrespect my uncle by telling him what I thought of that practice(simply put, it was and is evil).
Fair enough. I would be interested in what you find out from your family. If you don’t post here, ping me a private message please.
I admit my knowledge of Polynesian cultures is sketchy. I have found out recently that some of the Central American peoples were at least in part Polynesian, sort of validating Thor Heyerdahl’s theory, except that he had the direction of migration backwards.