I think you're talking about survivor bias, not Berkson's paradox.
Also the study intentionally focuses more on the cost-benefit of retaining a specific population - productive toxic people - and doesn't care about non-productive (toxic or non-toxic) people since they don't factor into that specific C/B equation.
I think the reference to Berkson's paradox is spot on:
> The most common example of Berkson's paradox is a false observation of a negative correlation between two positive traits, i.e., that members of a population which have some positive trait tend to lack a second. Berkson's paradox occurs when this observation appears true when in reality the two properties are unrelated—or even positively correlated—because members of the population where both are absent are not equally observed.
But you are also correct, survivor bias can lead to Berkson's paradox.
Also the study intentionally focuses more on the cost-benefit of retaining a specific population - productive toxic people - and doesn't care about non-productive (toxic or non-toxic) people since they don't factor into that specific C/B equation.