That seems like a complete non sequitur. This is the model explaining the rest. Obviously the explanation is not very interesting since the Towers of Hanoi is not an interesting problem. But that's on the researches for choosing something with a trivial algorithm if their goal was to test reasoning abilities.
Because that wasn't the task given to them. It's like giving a student a test and you asking them to solve an equation and they give you the general form. It's incomplete