New Zealand under performed this year as well at U20.
As for the current No. 1 rugby playing nation according to Hansen. IRELAND U20 had the humiliation of playing 11/12 playoff against Japan for relegation to 2nd teir.
I don't know if U20 is a really good indicator for the National team.
The final was between France and England. Won by the home team France. What U20 does show is that the Northern hemisphere teams have caught up to and now might be stronger than the South.
I actually think at both levels, there is not too much between any of the top teams, and on their day anyone can beat anyone. Just what you want at Test level.
That's one year you're talking about - we haven't figured near the top for 8 years which is a little bit of a different situation.
So, in the interests of fairness and having complete facts before us:
2008 - 1. NZ, 2. England, 3 SAF, 4. Wales
2009 - 1. NZ, 2. England, SAF, 4. Australia
2010 - 1. NZ, 2. Australia, 3. SAF, 4. England
2011 - 1. NZ, 2. England, 3. Australia, 4. France
2012 - 1. SAF, 2. NZ, 3. Wales, 4. Argentina
2013 - 1. England, 2. Wales 3. SAF, 4. NZ
2014 - 1. England, 2. SAF, 3. NZ, 4. Ireland
2015 - 1. NZ, 2. England, 3. SAF, 4. France
2016 - 1. England, 2. Ireland, 3. Argentina, 4. SAF
2017 - 1. NZ, 2. England, 3. SAF, 4. France
2018 - 1. France, 2. England, 3. SAF, 4. NZ
I'm not sure that the table above indicates that "there's not to much between any of the top teams", because the same teams always seem in the top 4.
England, South Africa and New Zealand have been in the top 4 every year since the event started.
I don't think that the evidence supports your point about the north catching up to the south - except that one of the SH nations has declined significantly.