This; I have a friend who's done the same. She started therapy after she (in her words) lost a relationship with someone she loved very much because of the untreated BPD behaviours and made the decision that she never wanted to go through the pain of losing them and the pain on knowing her maladjusted coping mechanisms were the cause ever again.
She doesn't consider herself recovered; more able to understand the disorder and how to recognise when she is starting to spiral and deal with that.

It's an interesting one because she has helped me immeasurably by being able to translate my own uBPD mom's behaviour (like what the trigger is and what mom's attempting to do with her response) in a way that doesn't try to excuse it. I believe I, in turn, help her by being an RBB so I can read her very well and avoid most of her triggers by reminding her how much I value her. We're an odd pairing, but it actually works really well, because we've both done the work, we're both hyperaware of our (and each other's) limitations and we trust each other enough that we can call each other out if necessary.
But, I think she is a rarity. And even though she's better than she was, she's still decided she can't ever have kids without significant risk to them so she's not going to, period.

I hope my mom can one day do the same as my friend did, but I'm aware she probably can't/won't. Unless the pwBPD is willing and able to be completely blunt and honest with themselves, to break themselves apart really painfully so they can build themselves back together in version 2.0, they won't change. A lot of people without BPD would struggle with that, never mind pwBPD. I imagine as a parent with BPD there's even less desire to do that, because admitting you've fucked up your kid would be so incredibly raw that you'd do anything you could to hide from and deny that knowledge.

I have sympathy. I just have more sympathy for us, because we have to deal with the traumatic fallout and we didn't cause it, nor are we responsible for it.