Not really the same as there's nothing to suggest the Storm would definitely get more at Etihad than at AAMI. Their last prelim at Etihad was 27k, and the most they ever got was 33k I believe.
Holding the Prelim at SFS instead of ANZ could lock out up to 25k fans, which is against why NRL changed it in the first place. As a TV viewer I'd rather the SFS go out with a packed Roosters v Souths/Dragons prelim, and I don't think holding the prelim at ANZ would crack 60k, but if the NRL are consistent then they would move it to ANZ. They moved that Tigers v Dragons 2011 game to ANZ and it only got 45k.
Preliminary Finals crowds since 2010 -
2010
Titans v Roosters at Suncorp - 44,787
Dragons v Tigers at ANZ - 71,212.
2011
Sea Eagles v Broncos at SFS - 31,894
Storm v Warriors at AAMI - 28,580.
2012
Storm v Sea Eagles at AAMI - 25,543
Bulldogs v Souths at ANZ - 70,354.
2013
Rabbitohs v Sea Eagles at ANZ - 44,546
Roosters v Knights at SFS - 37,752.
2014
Rabbitohs v Roosters at ANZ - 52,592
Bulldogs v panthers at ANZ - 46,168.
2015
Broncos v Roosters at Suncorp - 51,826
Storm v Cowboys at AAMI - 29,315.
2016
Sharks v Cowboys at SFS - 36,717
Storm v Raiders at AAMI - 28,161.
2017
Storm v Broncos at AAMI - 28,821
Roosters v Cowboys at SFS - 28,108.