I think you have a point 2B since its a one off game, I doubt anybody went "screw this then I'm not going". Different story in Wellington when you risk annoying those fans who you rely on to turn up every week.
I just don't think it would actually get people to the ground either. So all it does is use up column inches on a negative story. For a threat to work it needs to be credible. Which means actually carrying it out next year and not giving them a game, then bringing the game back to Auckland a season later. But as you pointed out, that's quite a risky move.
There is also the issue of one person not thinking their attendance will make a difference. They figure either enough people turn up or they won't, ultimately their attendance won't affect things (kind of like some people's attitude to voting). So a threat like this hardly changes their mind.