First thing first i didn't mean to offend anyone,second thing second since you know a lot about BPD and Bipolar i will state based on a research the main difference:

Experts note that one of the main differentiating factors between bipolar and borderline personality disorder is that symptoms of personality disorder are pretty consistent and ongoing, while people with bipolar disorder appear to have “breaks” between their extreme mood swings, in which they experience a mid-range

I again didn't mean to offend anyone i was just stating my own idea which i'm free to do it from the experience peace love and happiness.