Right. That “PSCA” is something else. As far as I can tell, DxO hasn’t created any documentation yet to explain why you’d want to enable Soft Proofing when both the monitor and destination are the same (typically sRGB, as this color space is small enough to consistently require decision-making by PL or by us concerning out-of-gamut colors). I haven’t seen any mention of the PSCA in the manual or elsewhere on dxo.com. I’ve only seen it mentioned in the forums, but its effects are obvious in cases where it makes a difference. So we know it exists and that it’s part of the export rendering pipeline that Soft Proofing lets us see.
We are waiting for DxO to explain that publicly. But see here for the discussion and a request to change the behavior: