This is untrue. In New Zealand we locked down a reasonable amount for the information we have on the case. With the current lockdown, there was a single case with no known link to the border which had traveled around the country while infectious. Knowing just this and that every case in managed isolation (iirc) was is the Delta variant, we went into lockdown.
Also, '5 lockdown' is misrepresentive. We can see on this page
https://covid19.govt.nz/alert-levels-and-updates/history-of-...
that while some lockdowns were very restrictive, country wide, and long (2.5 months), most were short and regional (with other regions maybe going to lvl 2 alert)