I don't think he HAS to play in a 4-3-3 (nor do I understand this obsession with formations in the fluid world of modern football).
It was simply giving him the license to roam and pull away from the congestion in front of goal that produced the goods (as well as playing against amateur kebabs). He can do that in lots of different formations - including the fabled 3-5-2.
He could do that in a 352 but not with peluso and isla as wingers. Giovinco also likes to drop sometimes, a la tevez... but it seems it drains a lot from him. IN the end of the trabson game he was really exhausted, but i think it had more to do with him being desperate to score.
He was SO desperate that in the Vidal goal, he was already mad that his shot got blocked...then vidal came and scored on the rebound...and instead of celebrating, Giovinco was like

, still thinking about his shot blocked.