Here's a quick rundown of the operation (taken from the manual).
Below I have animated the images from the manual. A few of my comments on the operation... This is a spool valve. It is not based on the GEO drivetrain. It is not a poppet valve. All of the seals are axially sealing o-rings. There are no face seals (or "poppets"). The manual chooses to call the center stalk a poppet, but it is not actually creating a face seal.
Two key features of this design are the fact that it seals the dump chamber when the firing sequence is initiated, and it that it has a 2 stage bolt speed profile (starts moving slowly and then rapidly speeds up on the second half of its movement). The first is important because sealing the firing chamber is critical for efficiency. The second will allow the gun to deal with misloaded or jammed paint very well.