Back to the original question. I have a variety of airplanes. More since modern radios stopped crashing them for me. I tend to set the high elevator deflection really high and low for nice flying. With the high setting almost every airplane that has sufficient power can be put into a loop and held there. As I gradually increase the elevator deflection there will come a time when the airplane will snap.

Conclusion is that there are a lot of things that don't cause the snap roll but might help it out a little. Among the helpers are prop torque, prop wash, one wing heavier, asymmetric aero forces from any asymmetric configuration effects. etc.

But the big and main factor is that the wing stalls. Things in nature and models being like it is, one wing will always separate before the other. It results in a snap.

The 60 just enables the airplane to carry energy into the maneuver better, keeps the speed up and allows the elevator to be more effective such that it will hold the high angles of attack needed to stall/snap.