The diagnosis/definition of BPD, is based on observations of several of signs or symptoms. Amongst these symptoms is difficulty getting along with people/being hard to please.

Given that being hard to please is in the definition of BPD, it is expected that people diagnosed with BPD are hard to please.

It seems many psychological disorders are defined/diagnosed by the presence of clusters of symptoms. eg, XYZ disorder is the occurrence of a cluster of symptoms. Stating that XYZ disorder, which is a cluster of symptoms, causes a cluster of symptoms is a circular reference, and therefore illogical. We don't know what causes the symptoms.