Redundancy may be the method they implied. I've seen it happen to my partner and several colleagues. It's laughable how easy it seems to tailor a redundancy to 1 or a few specific people, and the cost of fighting it is not worth it.
Faux redundancy is indeed a tool that can be used by smaller NZ employers. It's risky though for bigger companies to try it and it would never work for the homogeneous group that is Uber drivers, since they all effectively fill a single identical role, and redundancy must be about the role, not the person(s) filling it.
In this particular case I think this might be a bit of a red-herring discussion for Uber. I doubt they care about the drivers for reasons that aren't legitimate for firing them. For example, if the driver isn't getting enough rides to justify paying them they probably are redundant.
In New Zealand it's illegal to make someone redundant and then hire back someone into the same position for at least six months. You don't make a person redundant, you make a role redundant. This would be hard for Uber to do with drivers.