And square on you have Marshall, Ambrose, Walsh, Croft, Clarke, Willis, Fraser, Proctor, Imran - pre '78/9, McGrath, Hughes, Srinath, Lillee/Bishop/Bond/Reid (post injuries), Clark, Ntini, Ishant, Flintoff etc etc etc
They all have one thing in common, they took a stack of wickets
Bottom line is that there is no one way to get the ball from one end to the other effectively
Square on refers to the position of the hips at delivery
In the old days, coaches would have you believe that you had to be side on to swing the ball.
Guys like Marshall and Imran disproved that myth and proved that it was largely due to wrist position rather than trunk rotation