Can neuropsych test results be wrong?

Here is some background and the reason he was tested:

My DH has been complaining for several years about memory problems. At first I brushed it off, but in the past 2 yrs I see it for myself. Other things that concern me are

1. his difficulties in dealing with his phone and computer. He was always way ahead of me with technology, and my go-to guy when I needed help. Now, he calls me to help him out.
2. He has a hard time processing what he hears, for example when we're watching TV, I often have to put it on hold to expain what is going on. He says they talk too fast. Subtitles don't help.
3. Driving - he often tells me he feels too foggy to drive. This from a former, self-proclaimed control freak - he always felt more comfortable behind the wheel.
4. Very wide mood swings and some personality changes.

The list goes on, but you get the idea. DH wanted to be tested because there is a lot of Alzheimer's in his family and he is acutely aware of his difficulties.

The geriatrician gave him the shorter test and said he has MCI. The MRI was "unremarkable."

The neuropsych said he is fine, and in fact is in the 90th percentile for his age group (he is 72). DH and I are both skeptical. We live in a 55+ community and are quite sociable. DH has such a hard time with word finding that he is embarrassed to talk to people anymore. I regularly interact with people our age and older and I absolutely don't seem him as being 90% cognitively better than our peers.

Can a smart person have impairment and still ace this exam? Has anyone here had a similar experience with the neuropsych testing?