Just saw an article on MacRumors stating that an Apple memo to stores states that iPhones with 3rd party screens no longer void Apple warranty, as long as the 3rd party screens didn't cause further damage.
When a customer with an iPhone that has a third-party display seeks a repair for a non-display issue, Apple Stores and Apple Authorized Service Providers have been advised to inspect the device for any fraud or tampering, and then swap out the device or replace the broken part based on Apple's in-warranty pricing.
iPhones with third-party displays must still be within their warranty coverage period, whether it be Apple's standard 1-year manufacturer's warranty or extended AppleCare coverage, in order for warranty service to be honored.
If the presence of any third-party part causes the repair to be unsuccessful or breaks the iPhone, Apple said customers will be required to pay the out-of-warranty cost to replace the third-party part, or the entire device if necessary, in order to resolve the issue that the iPhone was initially brought in for.
Apple Authorized Service Providers are still instructed to decline service for any iPhone with a functional failure related to a third-party aluminum enclosure, logic board, battery, Lightning connector, headphone jack, volume buttons, mute switch, sleep/wake button, and certain microphones.
The full article is here: MacRumors
it does say that they have only confirmed it in the USA and Canada, but other regions are likely to be included. It would be interesting to see if that includes NZ.