I think they just had a good year of talent, I still think NZ is now behind England in terms of youth development (well everyone is).
Yeah but it was more than that. They specifically selected and then trained for size and strength:
"The national Under-19 tournament in Taupo last year meant we got to see the guys in context, at a high level, and got to focus on their work-ons and areas to improve like weight, size and strength," said new head coach Scott Robertson.
"Some guys have made massive shifts. So overall in our body-mass, we are bigger in that tight five."
Into that category comes Canterbury lock Hamish Dalzell - whose mother is a Whitelock - already standing over 2m, who has packed on 12kg, Auckland second-rower Jamie Lane, who is more than 10kg heavier, while openside Mitch Karpik, who was 92kg, is now over 100kg.
New Zealand had a set-piece clinic from South Africa last year, and so the size and techniques of the tight five are under the microscope.
Robertson and his assistants Leon MacDonald (attack) and Tana Umaga (defence) will name the 28-man squad for the Junior World Championship after the Oceania tournament.
From that article, NZ have an under-19 domestic tournament.
The um-ing and ah-ing over whether Oz should have U19 or U20 matches shouldn't be a big deal. Just call it under 20 (with full caffeine scrums) but make sure there are still enough players selected that will qualify for the following year's JWC.
The playing side of it is important, but so is the physical training.