All in all a lot of fun

Waves are always changing shape.

To have a vehicle those shape can be changed, as you surf it, is quite an advantage.

Of course the "absolute shape" of the mat is determined by it's creator "At the factory", so to speak.
Mat makers spend a lot of time measuring and tweaking the internal structure of a mat. Since the mat is surfed under inflated, that is not filled to capacity, the absolute shape of the mat is not used all at one time. The mat rider reshapes the mat as they ride along responding to changes in the wave.

By squeezing the forward outside corner you shift air from the outside rail to the inside rail. The inside rail forms to its absolute shape and the back of the mat flattens out to allow very clean release.
When you lift the outside corner of the mat you are reshaping the mat diagonally across the bottom as well, creating a craft that is now temporally reshaped to turn into the wave.

Pretty neat

Variable Inflation allows to not only change the shape of the mat during the wave but to adjust the mat to the prevailing surf conditions. The mat is not intended to be surfed in a state of maximum inflation you can adjust the volume of air in the mat between waves. This lets you determine the basic volume of air in the mat and adjustments can be made for factors like the water temp and the size of surf that day. Since the mat is filled with air, it constantly adjusts to the wave surface. Smoothing the way as the mat slides down the inclined plane of the wave.

All this design and manual manipulation gets you a craft that, when combined with a decent wave lets the mat take off like a shot down the line.

Other types of mat manipulation including subtle shifts of weight, change of the riders' center of gravity, using your body and fines etc to allow for turns, stalls, and the odd sideways slide.

All in all a lot of fun