Reverend Mother Gaius Helen Mohiam ((great)grand)mother of people with other/genetic memories and nobody remembers?

In Frank Herbert's "Children of Dune" Leto (the later God-emperor) tells Jessica¹:

They know you’re a Harkonnen! It’ll be in their breeding records: Jessica out of Tanidia Nerus by the Baron Vladimir Harkonnen. That record accidentally made public would pull your teeth to—

Jessica already should know this. As a reverend mother she should be able to peruse the memories of her female predecessors. Later in the book she considers the need and (im)possibility of testing of her granddaughter Ghanima: "There was no way to send the pre-born before a Reverend Mother Gaius Helen Mohiam"

In the much later published prequels by (by Brian Herbert and Kevin Anderson) Mohiam is put forward as the mother of Jessica, and this is supposed to be in the older Dune Encyclopedia as well, as mentioned on wikipedia.

I find this hookup unconvincing. Would Jessica not have known that Mohiam was here mother based on the memories she would be able to access after having gone through the spice agony? Or did I skip some plausible explanation for that.

And if Jessica would not know, then Alia should know as a pre-born. And when she and Mohiam meet in "Dune Messiah" no mention is made of this realisation by Alia (who did know who her father was wenn she killed the baron). In Dune Messiah the encounter is described with:

The Reverend Mother refused to look at Alia, but the words burned in her mind. Yes, far deeper implications lay here. The sister was an abomination, true, but there could be no denying her status as a Reverend Mother with all the title implied. Gaius Helen Mohiam felt herself in this instant to be not one single person, but all the others who sat like tiny congeries in her memory.

And earlier Mohiam is not so lofty about Jessica:

"That traitorous bitch,” Mohiam said, voice level. “Would I might disown my own hands which trained her.”

Would you say that of your own daughter, or if you had to would you not regret having given birth to her, above training her, and complain about that.

Reverend Mother Gaius Helen Mohiam is mother, grandmother and great-grandmother of several people with other/genetic memory and nobody remembers her, not even while meeting her. Mohiam never seems to think of those people as her "offspring" in the original books².

Did I miss any hints in the original books about Mohiam being the same as Tanidia Nerus?

Is there any explaination in the original books, about why none of the people who should know (Jessica, Alia, Leto II, Ghanima, Paul?) ever comment on this "fact". Or is it just the simple case where Mohiam adapt that name after giving birth to Jessica (so it would not be transferable in memory), and would that be enough to hide her identity³?

¹ _{Page 93 of the NEL paperback version. In the chapter starting with "And he saw a vision of armor"}

² _{Those written by Frank Herbert}

³ _{IIRC the prequels already call her Mohiam before her encounters with the Baron, so that could not be an explantion when observing the extended series.}