Yeah, as Darth Thor already pointed out, Anakin has officially been conceived by the Force.
Nope. It's deliberately left ambiguous.
I remember some years ago one of Vader comics alluded to him being created by Plagueis and Sidious, but then one guy from Lucasfilm story group (Matt Martin I think) immediately clarified that was not the official explanation of Anakin’s birth.
Just shows how big of hacks these guys are. Anyone while it may not have been the intent, anyone with some even basic understanding of SW and who was paying attention to the comic should have picked up what it seemed to suggest.
Btw even if Plagueis learned about this power from the witches and used it generate Anakin, why would it make him less special?
Because it removes the uniqueness of Anakin's birth. I also hate the idea that Plagueis learned it from the coven. The point was that Plagueis, being the culmination of a thousand years of Sith teaching, was so knowledgeable and powerful he was able to master life and death to such a degree that he even discovered how to create life. But now he might have just learned it from a backwater cult of witches. It's lame.