I looked at that picture again. Notice that the glove does not have the usual outer layer in place - you can see the inner workings of the glove.

The metal ring joint at the wrist connects to a gimbal joint inside the wrist of the glove, out of view.

Look at the back of the hand. The white you see is the restraint layer, not the pressure layer. Notice the strap across the back of the hand, with the buckle. That is for tightening the restraint layer against the palm of the hand, to prevent ballooning.

Mechanical aids indeed.