

In any case, people should start viewing IQ testing as “cultural testing”. We know it doesn’t really capture “intelligence” but a western way of thinking about things. So basically some twins are more educated in western thinking than their siblings, and it has to do with their upbringing into the culture. Not surprised.
Not necessarily the topic itself, but many factors affect IQ tests performance. Our perception and assessment of the world around us is strongly biased by our culture and education. The one factor you mentioned being the language is amongst many but its relevance should not be downplayed.
I admit I wrote that comment being reductionist. Mostly because IQ tests and the conversation around them is often reductionist too, and lends itself to western elitism. The history of the study of intelligence is terrible and we should be better at dealing with the topic these days.
Some examples of bias: https://neurolaunch.com/many-intelligence-tests-are-biased-in-that-they/ https://www.science.org/content/article/what-does-iq-really-measure