I can confirm its him...I was on set as a extra last week and got familiar with who were regulars on set and the Atl twins are always there since they play drug dealers in the movie
here is there recent tweet:
Sidney & Thurman @TheAtlTwins
We're having an amazing time on set with James Franco, Selena Gomez, Rachel Korine, Vanessa Hudgens & Ashley Benson! Harmony is Killin it!