I think Illawarra Steelers fans would probably claim 1 premiership, as the fact they were not supporting the St George Dragons before STGI means this is the first premiership a team they support has won the comp. They can claim 16 if they want but I am not telling them what to do.
As a St George Dragons supporter before STGI, I will claim 16 because the Dragons teams I have supported since birth, have won a combined 16 GFs. 15 as St George and 1 as St George Illawarra.
As the official body (News controlled) NRL has Saints listed as 1 premiership, you are quite within your rights to back them as any non Dragons fan would. But if you expect me to swallow their offical line, forgive me if I reach for the grain of salt.
The NRL claims all history of the NSWRL competition stretching back the first comp (rightfully I believe), despite the NRL only existing since 1998. So by that rationale, the combined history of the teams know as the Dragons (STG and STGI) should also be combined, ie 16 premierships for a team called the Dragons .
And before someone throws up the situation of the Wests Tigers and whether their previous titles should count for the Wests Tigers, I dont think their premierships should be combined. They are not the Western Suburbs Balmain Magpies or the Balmain Western Suburbs Tigers, playing in the same jersey as before. As such they can create new history as the Wests Tigers.
St George Dragons becoming part of the St George Illawarra Dragons is a much simpler decision when it comes to recognising the combined history(of 16 titles). Makes it more black and white when you consider Illawarra did not win 1 comp on their own. So I am not claiming titles to which I am not entitled.
Before anyone thinks I am denigrating the great Illawarra, I assure you I am not. In 2010, we could not have added to our previous 15 without the great contribution from Illawarra (and Wayne Bennett of course). I will forever be thankful for our South Coast brothers.