The strength of the author’s examples is irrelevant. We’re focusing on whether the author’s reasoning for arguing that students should have access to textbooks during exams is sound.

The effect the author’s recommendation would have on test scores is irrelevant to whether the reasoning in the author’s argument is sound.

We don’t know if the author took this into account, but regardless, the fact that professionals were once students has no bearing on the strength of the author’s argument that students should have access to textbooks during exams.

We don’t know if the author took this into account, but regardless, the fact that professionals have devoted years to studying one subject has no bearing on the soundness of the author’s reasoning.

This describes a possibility that the author ignores. If the purposes of evaluation in the professional world differ from those in school, it may be well-reasoned that students aren’t allowed access to textbooks even though professionals have access to reference materials.