When I was LDS, I remember being told that Heavenly Mother’s name was ‘too sacred’ to be known. That Heavenly Father loved his wives too much to tell us because we would blaspheme them by taking their names in vain.
So, based on your post, I grabbed my Pearl of Great Price and checked the fascimilie notes.
Fascimilie B - which the site claims has the name of Heavenly mother (at least one of them) is not included in the PGP, nor I had I came across it before other than this site even at the BYU archives after the ‘discovery’ date.
That said, it is possible that the document exists and that Smith ‘translated’ it, however given the ridiculous statements on the site, I would prefer independent examination of the document.
Apparently Brigham Young taught Adam is Heavenly Father, and that his wife Eve is Heavenly Mother: “I tell you more, Adam is the father of our spirits ... our spirits and the spirits of all the heavenly family were begotten by Adam, and born of Eve. ... I tell you, when you see your Father in the Heavens, you will see Adam; when you see your Mother that bore your spirit, you will see Mother Eve.”
Was Young teaching this before the plural marriage teachings came about? I know little about the LDS so have no time line to go by.