Interesting comments from John Bracewell on radio about NZ quicks coming back for multiple spells, and the way SA lower order took the game away from NZ in 2nd innings.
So I compared opening bowler workload at the time of 7th wicket falling in both 2nd innings:
NZ 7-188, Rabada had bowled 19 + 15 = 34, Jansen 22 + 14.1 = 36.1
SA 7-219, Southee 32 + 19 = 51, Henry 35 + 18 = 53. Then SA tail wagged, adding 135 runs in 21.4 overs.
Showing (1) the long innings by SA top 3 on day 1 took some of the legs out of the NZ seamers, (2) NZ batters didn't tire out the SA quicks in the same way, but also (3) Elgar's use of Maharaj as a stock bowler, which reduced workload for SA quicks, compared to Latham who didn't use de Grandhomme + Mitchell the same way.