Hi Turkish,
Yes, I remember my uBPDxbf told me something very similar, and to accomplish that he admitted that he would pick the thing he knew would inflict the most emotional pain possible and tell me that. To hear him admit that actually made me feel better and also made it easier to cope the next time he would say something demeaning, hurtful or cruel.
Did your x feel that it was a relief to be called out on what might possibly be causing her anger?
Maybe, because I asked her, rather than "abandoning" by walking out as I used to do. Sometimes she would flat out reject me asking, and shut down angrily, but that's BPD. Sometimes she would walk out of the house in shame for a while and then come back, bemoaning how she hated it when she treated me and the kids like that (she didn't so much lash out at the kids, though she did twice at S then 3 before she finally left, as it was them witnessing her behavior).
I may be fooling myself a little, but I think part of her leaving me was her shame in treating me like she did, and also not wanting the kids to witness it, so she "had to leave" as she put it. She always said I was better with the kids. She still thinks so (and it's true).