See as I am laughing very loud as I am reading through your post, this is because this very topic is what I experienced in my grandmother's house where I grew up. She never allowed me touch that part of chicken (gizzard) she said it was not for children, and it wasn't just gizzard, she practically stopped me from eating boil egg, saying that it will make me spoil, that any little child that eat full egg will definitely become a spoilt child, I wasn't bold enough to ask her the reason, I just believe and leave that way.

But in my father's house, when my mom prepared chicken, she will be the one to eat the gizzard and sometime cut it for us and my father will not even bother to ask about the gizzard or even place any value on it.

The same thing goes to fish head, people normally says that it the man of the house is permitted to eat the head of a fish but that's never applicable to my father because he doesn't eat fish head or make it a big deal.

It is true that all this rules and myth was a set up from elder men from the society to keep oppressing women and dominating over them as you've clearly stated... And I thank God for modernization, if not we would still be be leaving with this stereotype, meanwhile some part of Africa society are still upholding unto such myth, I pray may God deliver us.