It's all about looking to see what gives the team the best possible chance of winning... Primarily the world cup, but essentially winning all the time.
The club v's country debate is all about preparing the English team to have the best possible chance of winning.
Having a stable coaching team over a number is years would usually be seen as good preparation for that too.
Ultimately, one of the things that SCW said was that being the World number 1 team heading into a world cup meant that they had prepared the best of any other team and were in the best position to win.
If they weren't No.1's then essentially they'd won against the odds.
We all know there are plenty of problems with the ranking system, but the premise is accurate.
If you are a good team, winning all/most of your games against all opposition in the lead up to a world cup year then you've done a lot of what's needed to prove you can win a world cup.
In reality, that can happen 1 or 2 years out with a new coaching team, but more often it'd be good to show long term form over a number of years