Is the mother of a woman conceived through mistaken coitus (shubha) or fornication, or the daughter of such an act, a Mahram to the man involved?

Primary text

The mother of a woman with whom a man engaged in coitus under a mistaken premise, or the woman he fornicated with, or their daughter, are not Mahrams to him. This is because their forbidden status stems from a cause that is not permissible, and thus does not establish the ruling of Mahramiyyah, similar to prohibitions established through the process of mutual cursing (Li'an). Therefore, seclusion or looking upon them is not permissible.