It's probably the face of the man. On older style men including TS, the face was textured all the way up. On Tornado the horizontal groves stop on the upper part of the flat to help prevent stubbing the ball. McCloud hand carved prototypes where the texture was all the way up the face. The guys there in the shop complained the men caused them to hurt there wrist because of stubbing the ball and that it took all the power out of there pull shot. I cant remember if any plastic production men were ever made with 100% textured faces. But McCloud eventually listened to his employees and others and eliminated them. I think Murray told me he had a complete collection of men. When I see him again I will ask him.
As for why it is harder?
I beleave to shoot a good push you need a larger sweet spot to be able to square and cut back on the ball. The elimation to the texture on the face makes the sweet spot narrower than on TS. If you swing back shallow you can't pinch the ball on the follow through. The ball squirts out, sliding on the vertical groves not allowing you to put any power in your shot. It also makes cut-backs on the push really hard unless you pitch the ball way back on your follow through. It can be done but it is very difficult.