That's what is so stupid about it. It doesn't prove anything. People's plans can still change. Get caught in traffic on the way to the airport. Etc. Being checked in this early is no proof that they'll take the flight. I would go further and say it is a less reliable indicator than those who check in on the day.

How many flights will leave late because NZ tries to find people who checked in weeks or months earlier and are actually not flying?

If it worsens the on-time performance and worsens the seats I get, then I will not be happy with this at all.

Does anyone know if this is a deliberate move by NZ or just a (yet another) bug in their website?