I can't stress this enough; The Arcturian Heresy isn't accurate. Its a heresy.
I've seen this posted before, maybe it was by you though, but that isn't what the name of the book implies. It isn't saying "hey this book right here is heresy, don't believe it!". It means that the idea that Zurin is the Underking is heresy.
You are overlooking the fact that it would be rather silly if a book wanted to label itself as heresy. More likely is that the book's title refers to ...
By the way, who says a heresy is "inaccurate"? As far as I know, a heresy is just one dogma that's in conflict with the dominant, orthodox dogma. To say that a heresy isn't accurate, is to say that orthodoxy is valid (by definition).
Technically an enantiomorph is just two things that are mirror images of each other. In TES however the enantiomorph concept deals with 4 beings. There are two beings that are the enantiomorph, sometimes referred to as the king and the rebel. Then there is the female principle that the two halves of the enantiomorph fight over, ... There is also the shieldthane/witness who witnesses the events take place and is maimed in some way, physically or spiritually, and records the events...
I've seen this posted before, maybe it was by you though, but that isn't what the name of the book implies. It isn't saying "hey this book right here is heresy, don't believe it!". It means that the idea that Zurin is the Underking is heresy.
I can never keep these official terms straight, but this helps. I've been working on a theory, even thought it's not all hashed out.
Basically... I'm trying to synchronize the four roles in the enantiomorph, to the three guardian signs (Thief, Mage, Warrior), plus the Serpent. There's a few ways you can fit them together.
The rebel-betrayer is usually the Serpent (mobile/threatening constellation) or the Thief (naturally).
The king-defender is usually the Warrior.
The female-principle could be the Mage (knowledge/magic) or the Serpent (wily trickery).
The sheildthane/witness can be the Thief (stealth/watching), the Mage (scribe/knowledge), or the Serpent (hidden observer).
Sometimes, they seem almost to fit together, but never to my satisfaction. The other idea I've tinkered with is to drop the Serpent from the equation, and let the female-principle be a wild card of one of the Charge signs, possibly limited to one of the Charges under the king-defender Sign's domain.
Feel free to mess around with it - it's not quite done...