These types pf studies tend to get the results they seek. We are Post Science around here, and this kind of drivel is popular. A lot of these people involved in the research don't even have a clear definition of BPD or other disorders. Publishing nonsense like this gives the appearance they are studying it or somehow gathering insight. the reverse seems to be true, since they expanded the definitions of these disorders. They typically don't do meaningful research, like what the impact this kind of disorder has on family members or people around them. These researchers don't have much of an interest in expanding our knowledge, or even asking what else could contribute to that behavior.
Sites like this have done a lot of damage, spread a lot of nonsense, stigma and discrimination. It was really stupid to believe that research would lead to a new understanding or new insights, it has not. This is the kind of bogus and misleading research that is popular, and most important of all. likely to get funded. it is really no wonder that every indicator of mental health here in the US is showing a decline. This is not even science, it is marketing filler.