Talk about nonsense. Their method sucks. How can they tell when the difference occurred? And how do they know whether it was caused by male death or lack of monogamy?
This kind of speculation is mental masturbation. To know what works, look at the real world - ideally what works today but at least what has worked in history. Pushing genetic/racial homogeneity has never worked. Pushing cultural and religious homogeneity works. If you want to see this in...