Trump's communication is at such a child-like level that I would have expected impairment to show up on that test. I wonder if it's something that Trump prepped for, skewing the results. The validation tests are based on people going into the test not knowing anything about it. Yet the test is widely available online, so if someone went into the test not with the goal of accurately assessing his mental abilities, but rather trying to score well to address concerns others had, it wouldn't be hard for someone who was mildly impaired to score well. It's an extremely short test, so it's not like, say, an SAT or an hour-long IQ test, where a mildly impaired person couldn't memorize all the answers.
http://dementia.ie/images/uploads/site-images/MoCA-Test-English_7_1.pdf
For example, if someone with mild dementia is taking that test, sees a picture of a lion, a rhino, and a camel, he might have trouble recalling the name of one or more of them, losing points. But if he took the same test several times for practice before going into the doctor's office, it's going to be easy. Forgetting the word "camel" is something that might happen to a mildly impaired person if he's had no use for that word for years, but if he's been using it repeatedly in practice, including directly before going into the doctor's office, then his dementia would have to be very advanced to lose that word.
Similarly, someone with mild impairment might have trouble remembering a series of words like "face, velvet, church, daisy, and red" hearing it just once from the doctor. But if he downloaded the test in advance and went over it repeatedly, coming up with a little song or other mnemonic device, that's going to be very easy unless he's really far gone.
It's not hard to picture how this would play out:
At first Trump announced he wouldn't do a cognitive test. But then one of his people pointed out that it's just a one-page test with only a handful of questions, and that they could get hold of it ahead of time -- that the doctor would be sure to administer the same most recent approved version of the Moca that every other doctor uses. After the team ran Trump through it several times, correcting his errors and giving him practice on the memory items, they were ready -- and they had nothing to lose, since he had full control over which parts, if any, of his exam are made public. So, take the test and if he does fine, release it, and if not, keep it quiet.