Twin studies can't prove something is caused by "genetics"[0]; twins are not free of environmental factors and don't necessarily have the same genome. Genetics, like many scientific fields that can't do real experiments, is just people abusing statistics for fun.

[0] if it did, this wouldn't mean anything, because it can't be used to make predictions, because you don't know if any random person X you are trying to predict trait Y of has these "genetics".