Experiment that ended in 1767 still linked to higher incomes, education levels
The study is still incomplete until you figure out whether the belief in God and specifically the bible are actually what helped retain the knowledge and work ethic over multiple generations and how it compares to atheist/muslim/[other religion] communities.
Instead we get a bold claim that education itself is enough to help people when maybe the bible or religious belief in general was a primary ingredient in that help.