Not convinced.
The last two world cup finalists had what, 6 and 12? NZ have 5. Or is that those other nations just have more talent than we do?
In fact the last winners were the most dispersed with a lot of their players playing in Europe. Does cohesion need to be built at club level?
His take on that was that the core of the Springboks side was made up of current and former Stormers players (more than half the team that played the final were current or former Stormers so they were a very cohesive side).
England has low cohesion generally because they are spread among a lot of clubs but the cohesion of the England team at the RWC was good because they were very heavily focused from a couple of clubs (8 players in the final came from Saracens and 4 of the starting backline were Leicester players).
World Cups are also a bit different because they bring teams together for a long time. It's why traditionally non cohesive countries like France and formerly Argentina outperform at RWCs because it brings their players together for a long time and they get better whereas they never normally have that opportunity.