The article Concussion Tests Won't Fix the Concussion Problem states,
"The rationale for baseline concussion testing makes intuitive sense — you measure people’s neurocognitive skills at baseline, when they’re healthy. If they hit their heads, you test them again to measure whether their memory, reaction time or other cognitive skills have changed. A decreased score suggests that something is wrong, and you take a closer look at the athlete (and perhaps do more medical exams) before you give her the OK to return to activity. The main worry is that the athlete will get another concussion before the first is healed."
"The problem is that the tests can’t tell us whether it’s safe for an athlete to get back in the game; they just offer something for teams and programs to show they’re serious about concussions. That something produces numbers, which makes it seem scientific. But the numbers may be giving a subjective decision — whether an athlete should return to play — a false veneer of objectivity."
“... there’s just no evidence that just because your score is back to baseline, your risk is, too,” said Robert Sallis, team doctor at Pomona College and a past president of the American College of Sports Medicine."
Dr. Christopher Randolph of Loyola University Medical Center said, “There basically are no data that would suggest that once someone has recovered from objective symptoms that you can detect anything with these tests,” he said. “They provide nothing more than a false sense of security.”
A 2018 paper looking at the validity of baseline testing found a "growing concern about the validity of baseline test results -- meaning there's concern over the degree to which the scores on these baseline tests actually reflect an athlete's true cognitive ability" MedPage Today.
"These findings suggest that the rates of invalid performance on baseline testing may be alarmingly high" and that the testing may "be of little use when making a diagnosis of concussion or determining when it is safe for an athlete to return to a collision sport...."
Dr. Douglas Comeau, a Boston University school of medicine professions sumed it up by saying, "PCPs [primary care providers] need to know that the younger a patient is, the less valid the results may be."