Is there a problem with this critique?

For 1, how is that a even critique? Is it possible for psychologists to have failed to understand something that cops understood? It doesn't even seem surprising that police, who have generations of practical experience dealing with abuse would notice the trend before ivory-tower academics.

As for 2, I don't think that suggests the effect is overstated, except maybe very weakly. The effect is so huge that it's hard to believe that police suspicion of step-parents can "explain it away".