Question

Hello Rabbi,
I came across a responsum of Rabbi Ovadia about a woman who had an abortion and then later became religious and got married. When her first son was born, her husband was preparing to perform the redemption of the firstborn, and she asked whether she was obligated to tell him, for the purpose of preventing him from making a blessing in vain during the ceremony. The responsum of Rabbi Ovadia (as brought in Yalkut Yosef) is as follows:
“A woman who, while she was secular, became pregnant through a forbidden relationship and aborted the fetus after the pregnancy was already recognizable, and after she repented married a yeshiva student, and they had a firstborn son, and she is afraid to tell him that she had an abortion so that domestic harmony not be disturbed—it is permitted for her not to tell him about the abortion, and the husband may perform the redemption of the firstborn; and even if she causes him to recite a blessing in vain, there is no prohibition in this, because of domestic harmony.”
Now, in the notes he explains why, assuming that a blessing in vain is a rabbinic prohibition, there is no obligation at all to prevent a person from violating this prohibition unintentionally. My question is this: if there is no obligation to prevent the husband from reciting a blessing in vain, why justify the permission with the phrase “because of domestic harmony”? Does that mean that Rabbi Ovadia thinks that even if this were prohibited, the value of domestic harmony overrides the halakhic prohibition? If so, does he have the authority to rule that way? And if not, isn’t this an unnecessary romanticization of Jewish law—as though the halakhic considerations are marginal compared to the moral values standing before the rabbi when he comes to issue a ruling?