If this argument is flawed, it’s the wrong flaw. The nutritionist assumes that a certain cause led to an effect. The cause (overeating) was removed, so she concluded that the effect (weight gain) was removed. By contrast, the principal observed that an effect (failing scores) was removed, so he concluded that the cause (bad teaching) was removed.

If this is flawed, it’s not the same flaw as the stimulus. The manager believes that a certain cause (different tasks) led to an effect (filing complaints). He removed the cause, and the effect disappeared. By contrast, the principal in the stimulus observed that an effect (failing scores) was removed, so he concluded that the cause (bad teaching) was removed.

If this argument is flawed, it’s the wrong flaw. The nutritionist is arguing that a supposed effect (weight gain) never occurred in the first place. By contrast, the principal in the stimulus argues that the disappearance of an effect (failing scores) means one possible cause (bad teaching) must have been removed.

The manager concludes that productivity must have improved at this office. His reasoning is that complaints have disappeared, and he thinks that lack of productivity causes complaints. This is flawed, because it assumes that only one cause could have produced this effect. Perhaps the workers are as unproductive as ever, but want to disguise that from the manager by not filing any more complaints.

Analogously, the principal in the stimulus assumed the observed effect (failing scores) could have had only one cause (bad teaching).

If this is flawed, it isn’t the same flaw as the stimulus. Once a certain cause (thinking of food) is removed, the nutritionist concludes that an effect (weight gain) is removed. By contrast, the principal in the stimulus sees that an effect (failing scores) is removed, and concludes that a possible cause (bad teaching) must have been removed.