No one will ever know if that is correct, but let's assume it is. You must also then acknowledge that Penrith has the largest junior district which the Roosters can not compete with so they must look at players outside their area, just as Penrith does and brings them into their system. Unlike my team the Dragon's which are a basket case at the administrative level which is reflected on the field, the trick is to continue to evolve and not rest on your laurels like the Dragon's did after the Bennett era. Enjoy the team you have as you never when it might end.
Penrith always had a huge junior base, but never really used it well until recently. We sporadically produced good teams every so often when we lucked on a set of juniors (I am being a bit trite, I know a lot of effort went into producing those teams. But history shows it was never maintained because the systems weren't in place to support it on an ongoing basis). Parramatta have also a huge junior base with similar results, although to be fair, they have made a few GF's.
The point is a huge junior base guarantees nothing. St George has a more than large enough junior base when you include the Illawarra region. But you have to have a development process in place to get value out of it. Your current press about Sullivan wanting to leave because his path is blocked points to a problem. Nobody is making sure he gets the game time to develop him and now he is frustrated. Bennett was a master at it. Always bringing through a baby Bronco who sure enough, two years later was playing SOO. He was ruthless, sacking Lewis, Jackson, Petereo and many others to make sure youngsters could come through. But he did it in a managed way.
The Roosters may not have a huge junior base but they develop players and invest in coaching and support to bring through players, regardless of where they were born. It is telling that the GM that set up their development pathways was Gus. Watchout for the Bulldogs in the next few years,they are going to become a force.