Yeah, from speculation I'm pretty sure it was once used in caricatures of "The Black Man" to imply he was too poor to take care of his teeth, which left them all crooked. I cant be sure. I CAN say though that giving Chinese people big buck incisors IS a racist stereotype. Maybe its a shared thing?
Rory might be giving people tooth gaps because uwu everyone is different uwu which happens all the time. Teeth are one of those things that artists like to fuck around with, and (slight powerlevel) I'm guilty of giving humans stupid looking teeth on occasion, too. But if Rory is reserving stuff like that only for black characters then oh my, Rory dear, how very
unprogressive of you