I read that over 10 years ago and can't find it. So either look yourself or ignore. Can't back that up.
But if you are around BPD forums you will often hear that two BPD people have had more success and longer relationships than usual. Depends of course on the people and how their condition differs individually. It can also go in the entirely opposite direction. Imo many people diagnosed nowadays with BPD are 'not really' BPD, at least not anywhere near as severely as it used to be diagnosed. They just have whatever issues that fit nowhere else. It has become kind of a sink for having some 'personality disorder not-yet-invented'.