Kia ora,

I have to wonder if this policy was used to evict people in Tāmaki to make way for the gentrification underway there.

The Tāmaki Regeneration Company (Joint Govt and Council) gave a promise that state tenants displaced during the developments would be able to remain local and be rehoused.
below is a quote from the CEO John Holyoake from 2016 so the number probably went higher:

"There’s the scourge of “P” contamination. Holyoake confirmed 20 homes are empty in Tāmaki not because of imminent demolition but because they are poisoned by methamphetamine production or use"

That would given them a nice easy way to get people out without the bad PR ala Niki Rauti and not honour that promise.