How the NFL and NRL were formed were completely different. The NFL were an amalgamation of 2 competitions, the NRL isn't an amalgamation but a continuation of the NSWRL with new teams invited to play at certain points of its evolution. Although that is not to say that the QLD comp was not strong in the days when Lewis, Meninga, Miles, etc played in it.
Well technically the NRL was a amalgamation of the ARL and Super League in 1998. But not exactly my point. I don't think anyones arguing that the NRL is essentially a continuation of the NSWRL. And as a result I think they reserve the right to record history however they like, and that's what they've done.
The only reason I brought up the NFL was to show an example of a line in the sand has been drawn and applied in the history books without completely erasing the prior history.
My point is that at some point the NRL became a national competition where you had 100% of the top tier talent playing across a single competition, not split across multiple competitions. Hence from a competition perspective you can unquestionably say that the team that wins the premiership is the most deserving team in the country to hold the title. Personally I think a premiership won now should be seen as a greater accomplishment than one won in 1908 for a number of reasons. If I was a Souths fan I might have a different view.
There were still players being selected for NSW, QLD and even Australia from non NSWRL teams in the 1980s. So its not out of the realms of possibility that some of those teams could have challenged the top sydney teams. Given the interstate results, it might not have been often, but we'll never know. So how can you devalue a 1st grade premiership in an 'equal' competition of the time?
In Australia though its not so much an issue, as off the top of my head only the Dolphins and PA Power are teams that have history that predates their inclusion into the NRL/AFL? Am I missing an others? I can't see them changing the rules for 1 or 2 teams.