He wasnít off balance, he felt the arm and collapsed his feet. Simulation isnít just diving with no contact, itís also exaggerating a fall to gain an advantage. At no point does an arm touching your chest result in your legs collapsing, not naturally anyway.
I don't think it was the arm at all (which certainly wouldn't have made him fall forward). I think he was either tripped or was pretending that he was tripped. Newell seemed to make very slight contact with his left foot, maybe even standing on his toes. Dobbie went down too easily though.