That is just false abCaspeRR.
Sims 3 stressed my old 6850 build. The more items, the larger the lot, the more the Sims 3 is going to stress your computer. You might get away with dedicated graphics at medium settings but you'll see lag when speeding the game time to the max.
Sims 3 isn't that demanding anyways... I used to run it on a cheapy $250 laptop with a Celeron, 2GB of RAM and Intel HD Graphics 3000 and was able to pull off about 25fps most of the time. And you don't really need high fps for those types of games.