I don't think the above implied JB is a bad author at all. Storytelling is more important than world building, so an author needs to be able to break the rules. Assume an author builds a world that is based on a particular ruleset (like Salic law) but needs an exception for three different characters. Unfortunately, the author can't think of an exception that would govern each case and using three different exceptions would undermine the ruleset and raise questions as to why characters "A, who fits exception 1," "B and C, who fit exception 2," and "D, who fits exception 3" still follow the general rule. In such a situation, it is better for the author to just handwave the exception and focus on the story.
It's not the need for occasional exceptions that I consider to be the issue, it's the contention that "Salic law" is a plot device rather than a piece of worldbuilding. As I recall, there was
no reason to include the "Salic law" thing in White Night if it was inconsistent with what we've seen, because it served no purpose except as a piece of worldbuilding. If it was going to be a problem, then Jim could have just said that magical ability was usually inherited, as was established in Proven Guilty.
Therefore, I believe that:
A) As a piece of worldbuilding, the essentials of it are true.
B) Apparent exceptions are because Harry does not understand the nuances of it or does not know the whole story of what's going on.
C) Jim
does understand the nuances and
does know the whole story, so any apparent exceptions almost certainly have an in-universe explanation.
It's like the Darkhallow thing, really. Harry gives us an explanation of how it works, and we have a WoJ on how it works, and these are partially contradictory. This is not because Jim forgot what he said about the Darkhallow when he was talking about it later, it's because Harry didn't understand everything.
