You're a fool! At the SFS, if it rains, you will get wet if you are in the front level, unless you are right at the back!
Souths get larger attendances than Easts! What is good enough for Easts, is beneath Souths!
The back 15 rows at the SFS avoid the rain
And the corners
And the members
and the corporate area (which the Roosters open if its a large crowd and likely to rain)
and bays 24 and 26
So it's not just at the back
But yes - all stadiums in Sydney are a problem if it rains, the SFS and ANZ included. It's as if stadium builders decided years ago that it just doesn't rain here, so they don't need to bother with roofs, or if they do, they have them angled so that rain comes right into the stadium and soaks everyone.
ANZ is designed to hold 80,000 - if NSW packs it out for Origin and it rains, more than half the audience would be getting wet
At the SFS if there were 40,000 there around 50% would be getting drenched. They're both badly designed in that respect.
Luckily, both clubs have sufficient cover that if it does rain, the majority of the 10,000 that turn up can stay dry.