Yeah... patience can be a big part of Test cricket.... I don't have much of that

As I have stated.. NZ's innings viewed in isolation was a "good" test innings.... but everybody KNEW from the outset that Time was lost.. I predicted about 2 days lost.. and I wont be far off. Kane Williamson (and NZ team staff) knew that and so IF they were serious about WINNING they needed to play accordingly... assume there would only be 3 - 3 and a half days play. It was SILLY to bat most of 2 days for their one innings... they would have batted even LONGER if SA had not bowled them out.
You have to take 20 wickets to win a test match:
Even IF NZ assumed that they would only bat once... by squandering 2 days batting for a "slow but sure" 1st innings, they left only a day and a half (max) to bowl SA out TWICE!! That was VERY unlikely to happen. Even if today had been a full day's play. They may well NOT have bowled SA out, or bowled them out and still had to bat again.. with not enough time to make a target.
"Playing for a draw" is often a best result for "lesser sides".
NZ have aspirations to be better than a "lesser side" and in this case a draw assures a SERIES LOSS... so it was worth some risk to go all-out for a win.