The claim "Sulu was not under the control of the entity" is automatically false, because everybody was. Beyond that, everything about the way the heroes act is fully open to speculation. And as I outlined, Sulu being coerced to tell a lie had beneficial results for the beast - or do you forget what the direct result was?
When Chekov goes after the Klingons, against Kirk's direct direct orders, Kirk just sits back. But then Sulu claims Chekov has no brother - and it is at that point that Kirk sends not just Sulu but a Security team to do battle with the Klingons in order to recover the Ensign. A clear victory for (*).
Why should writer intent be relevant? I'm not interested in writing or other noncanonical paraphernalia. I'm interested in the Star Trek universe and the actions of the characters in that universe. The writers may miss the obvious at times, too.
Timo Saloniemi