A firearm barrel includes any forging, casting, printing, extrusion, machined body, or similar article that has reached a stage in manufacture where it may readily be completed, assembled, or converted to be used as a firearm barrel

  “firearm barrel” means the tube, usually metal and cylindrical, through which a projectile or shot charge is fired

It's not farcical. A PVC pipe is an extrusion that is "readily converted" into a tube that fires a projectile. It's clear as day. Have you never seen someone fire a "potato" gun and use PVC as a barrel?

https://www.youtube.com/shorts/tS2jKYbzsnA