Or, and hear me out on this, they just use a normal barrel like absolutely every other company on the planet.
Kind of.
The difference is that here the barrel consists of a liner (pressed from the outside) inserted into barrel and bonded to it. The barrel is unusualy large with 20 mm diameter.
A typical conventional barrel for a PCP is a one piece rod, drilled to a tube and drawn with a mandrel to create lands. Those barrels is usually 10-15 mm diameter.