Just like trump does he can fail a test miserably and just tell the doctors to say whatever. Like trump is 6,2 and 220 pounds... All bullshit. Who's to say trump even took it? A Dr would only test like that if they suspected some sort of serious mental issue.
And I guarantee Biden wouldn't fail the test questions listed out. It is telling a dog vs cat in a picture type shit. Those questions are the thorough cognitive test. It takes like 5 minutes. Someone with real dementia would struggle through it.