In my case, my pwBPD (FFw) has benefited greatly from "psychological knowledge" that is not "aimed at her".
In prior years she has done couples therapy with me and also done some individual work, yet by and large it all went "BPDish" at some point and she quit...of course blaming everyone else.
Well, she is now an elementary teacher in a school that pulls students from "bad areas". So...kids (2nd and 3rd grade) that are allowed to room free at night, or one kid had the dad killed in local jail and tons of police responses.
I've lost count of how many social services reports she has made (mandatory reporter stuff). Once I find out that has happened, I usually shift my evening to be fully supportive of her and double down on "fun family stuff".
Anyway, my wife has a real knack for motivating troubled kids. This kid needs praise...this kid needs to be in the front row...back row, sit in special seat..etc etc.
Her test score improvements are off the charts, to the point where principals from other schools are calling and asking about her methods.
Anyway, she was asked to join the "crisis team" that has special training to calm out of control children. Apparently there are only a few people in each school that are allowed/trained to physically restrain children.
Well...so lots of training with psychologists and then out of nowhere the random conversation starters from my wife are about the importance of validation...avoiding invalidation.
I had to keep my poker face when she started telling me about dysregulations and peoples amygdala getting all out of whack. Letting kids spend time in a "calming corner" and talking to them in 15 minutes or 30 mintues works wonders...
I can tell she has taken some of this onboard. Of course there is nothing wrong with her amygdala..but mine...oh FFs is all out of control.

The positive change is undeniable.
Bottom line. It's rare that I hear about pwBPD that go to therapy for themselves. However..."for issues with their sisters" or "work" or about someone else...that is a bit more common.
Best,
FF