OK, missed that AC, point taken and agreed. Indeed if a fault that is offered as an acceptable deferred defect is seen as not acceptable by a Captain refusing an aircraft, he has a moral responsibility to the next captain to be so invited to enter the fact that it has not been accepted and why. That then starts one of Tucs "audit trails" which will tell a tale, loud and clear, to those who follow it later. As to:
why he decided, off his own bat, that he knows better than the engineers what is acceptable and what is not.
I refer you to the statement that I made earlier:
If you don't like what you see you don't take it, whatever anyone else says.
His boss may agree or disagree with that decision, either way it was made, and recorded!