As said, it usually means while you may have some traits of cluster B personality disorders, you don't have enough for a full diagnosis. They'll likely leave it on, even if it's not totally current as it can be something to just keep an eye on in the future. Like if you do start to struggle with any of it, they've had it previously noted so they know it's not entirely new for you.
Definitely ask though if you want an explanation.
You could also have a read of the wiki about both personality disorders and the different clusters of traits. Borderline falls under cluster B.
I know for example for me they listed for a while that I had cluster A and B traits, as neither were enough for a diagnosis of either type. Now my diagnosis has since been changed, but the traits were accurate. It could literally be that it's just your self harm history and the black and white thinking that they are categorizing as bpd/cluster B, and that's why it is still on there more than anything else.
Again tldr; The idea with traits means that you just don't have enough for a full diagnosis.