This is interesting but not new. A study from 1973 found that monozygotic twins reared apart have mean absolute difference of over 6 IQ points, with maximum difference observed several times that. A 16-point difference would be less common but there would be no difficulty finding one in a population of a thousand twin pairs, especially with massive family and cultural differences. https://link.springer.com/chapter/10.1007/978-94-011-6129-9_...

Also, another commenter notes the lower-scoring twin had a life-altering concussion. Pretty enormous omission from this reporting.

Despite this single shoddily-reported example, monozygotic twins reared apart show much more similar IQs than unrelated individuals raised together, indicating that genetics are the dominant driver of IQ. https://www.gwern.net/docs/iq/1996-bouchard-2.pdf