I agree with your first point about the raging boner, but the "local" thing is not correct. There is no such rule. The Roosters, Sharks and Manly tend to get the SFS unless it looks like they can get a big crowd ... but Penrith, Parra the Dragons, Dogs and Tigers have all played home finals at both venues... and the Rabbitohs typically play at ANZ despite being the closest team physically to the SFS. They also make the Knights play home finals at the SFS, which is much farther away for their fans than ANZ. You can say that the NRL will make Parra play there because of the raging boner, or because there might only be one game in Sydney that weekend, but you can't say that there is any NRL rule about playing at the closest venue to the team because that is nonsense. If you looked at it over the last ten years and factored in crowd sizes etc you will find that the NRL gives exaclty zero ******s who the "local" team is.
BUT ... in the case of a potential Parra v Sharks round 2 final HB is probably right ... if only because the NRL would gamble that plenty of Sharks fans will make the trip regardless of stadiums and plenty of Parra fans will get off their cousins long enough to make it to the game.