I think if a layman picks a niche, and really goes into it, then the layman has a fair chance beating the professional in that specific niche. So, you are not wrong with this feeling at all. What professionals have in their favor is a higher level overview of the subject, and experience with similar subjects. Usually this means that while they might not know a niche in an out by heart, they can discover it very quickly, or consider things that are not fitting into that specific niche.
Also, these journalists might not be professionals at all.
That is also true in medicine, as a side note. If you have a specific combination of conditions, or a rare condition, you will know more about it than doctors. The good ones know this and accept it. The bad ones are offended you know more than they do in this area – or simply go into denial.
In the end, each body is a niche, which each one is uniquely positioned to know better than anyone else. But it’s hard to accept, for medical personal sometimes, and often for the patients themselves. They tend to want the doctor to be the all-knowing god.
Yes, medicine was specifically what I was thinking about! And it's a touchy subject, just as you mention. A patient, a layman, isn't supposed to know more than the doctor. It's a delicate situation.
Take all human knowledge as a whole pie. Out of that is, the experts only know 1/100 of a slice. We maybe experts in some minute context, yet there are so many that know so much more when removed from that context.
Or rephrased, that Person who has to deal with something 80 percent of their life knows more than the person having to deal with it 20 percent of their life.
Also, these journalists might not be professionals at all.