As I understand the intent of an inside isolation offense, a lot of threes does not seem surprising. As smallfrie said, I'd expect the threes to come off of passes back out from the C/PF when he can't get his shot. Since he's the only player on the inside, the other four are spread out around the perimeter looking for long jumpers when their defenders crash inside to help out. Essentially the offense of the Olajuwon Rockets or the Howard Magic. The idea on these teams is to surround the dominant big man with good outside shooters, as either the big man will overpower his defender and get layups and close shots, or he'll pass it back out to the set-up shooters to kill the other team from long distance if the other defenders try to help out.