I'm not sure about the Grande, however, auto-transmissions does rollback when the incline level is anything above 30 degrees when in drive mode. However, if you're not driving in 'D', the chances of rollback are low but present.
Corolla altis line-up does have a standard feature called 'linear start assist control' that may attribute to what you've experienced but I'm not sure of it as the purpose of this feature is very different.
I've no intensions of spark a war over this but just mentioning a few of my observations here for the sake of information.
The automatic transmission cars do rollback when in 'D' drive, here's real-world test. There's a pretty steep incline when going to high-land country club near peer sohawa, Islamabad. The entrance of this resort is pretty steep & close to 40 degree angle. Stop the car in the middle of the turning points and release breaks, the auto car will rollback - this is true for automatic transmissions for Toyota's GLi/XLi/Altis 1.6/Premio 1.5/1.8/Axio & Honda's City 1.3/1.5 AT/civic rebon/rebirth & all of 660 kei auto-cars.
Having said that, since Premio 2007 & Grande share same engine (in some regions) - so this rollback is possible.
Please don't drive there just for the sake of this test. LOL. 
Unless you're into scenic beauty like myself who enjoy being in nature. Jokes apart.
If you're not in proper gear, the AMT-cars (Suzuki auto cars) does stall too.
That's where I've tested Yaris so shared my thoughts on it.
For more details, check here & here.
My two cents.
Peace
