Who lost the most marks when cheating was stopped? Those of lower socio-economic status. Because those of such status generally engage in higher rates of criminal behavior [1], why is this presumed to be surprising?
It seems to me that the basis of the author's misunderstanding that leads to their surprise is the narrative of wealthy people being more likely to be corrupt on a per capita basis, which clearly runs counter to the statistics which demonstrate those of less economic means committing more crimes per capita.
It also runs counter to the fact that those of greater means have greater scores due to greater means, and thus less likely to need to cheat to have good scores.
Did you read the article? Here's the relevant parts:
The most likely culprit, it emerged, was that the "collective" and "petty" forms of corruption, as witnessed by Dr Borcan herself, had a curious effect: they might be paid for chiefly by well-off students bribing invigilators, but everyone benefited. It gave the poorer students "a free ride" to higher marks.
It also meant that when cheating was removed, the academic advantages of wealthier students became even more apparent. Cheating it seemed had provided a kind of levelling effect.
The more correct explanation would seem to be that wealthier students have other advantages - probably along the lines of test preparation, lower stress if it's anything as in the States - which allowed them to retain high performance once cheating was reduced.
I'm not sure from where you're deriving these narratives and counter narratives from.
That doesn't contradict his claim in the least. I don't think he's opposed to the notion that disparities exist in terms of competitive advantage.
The point is rather that such a result only comes as a surprise if one has a strong a priori expectation that rich people cheat more than poor people. Otherwise one would predict exactly this effect.
I don't follow your last point. Why can't both be true? That seems like a leap. The socioeconomic status can still be the predominant predictor of grades.
It seems to me that the basis of the author's misunderstanding that leads to their surprise is the narrative of wealthy people being more likely to be corrupt on a per capita basis, which clearly runs counter to the statistics which demonstrate those of less economic means committing more crimes per capita.
It also runs counter to the fact that those of greater means have greater scores due to greater means, and thus less likely to need to cheat to have good scores.
[1] https://www.bjs.gov/index.cfm?ty=pbdetail&iid=5137