Night moans (or groans) are known as Catathrenia.
My grandmother has mentioned that she might have them, but I have never heard hers.
I know I do. My partners and even friends at sleepovers have mentioned hearing them and I have, at times, been woken up and heard the end of me having one.
I did undergo a sleep study decades ago and so the results are likely in medical records somewhere.
Interesting that it was 7 young women.
Those females could also just be connected to the “source” of the original “condition” or, magickally, it could be a spell or glamour, as there have been a number of imposters and imitators of me over the years.
Vestigial does not heave to mean derived from a known animal, human, or land.