I can relate sis, This has been a myth we all grew up with in Nigeria and i am yet to know who proposed this myth.
The fact that is is generally accepted by all the tribes in Nigeria, not even only on Sundays but also on Christmas day.
I guess there was a time when Rice was a special meal back then in the days dat promted it to be eaten on Sunday and special days or maybe because it is generally accepted in all tribes.
Funny enough till day i still see my following this trend and i don't think am leaving it soon.🤣🤣🤣🤣. Who ever invented it thank you ooo