I'd say that it shows he DOES need one, but then, suppose we imposed that same requirement on Congress?

KJP Defends Biden Not Taking a Cognitive Test, Claims the Demands of His Job Proves He Doesn't Need One

Following the exam, a reporter questioned why a cognitive test was not a part of the routine exam that is given to most presidents. 

“Why not just have his doctor administer the test and then the case closed?" the reporter asked. 

In response, Jean-Pierre said"Folks need to understand that the president passes a cognitive test every day,” arguing that being the president of the United States is a mental health exam in itself. 

One that he flunks every day.