I’m sorry, but they’re right (and also a dick) - the songbird uses metal barrel liners for it’s swappable barrel unit block thingies (I have no idea what the technical term for those is. Bullet pods? idk.). The pure nylon ones used .22 cartridges (this was the pre-liner phase of the design) and had a 50/50 chance of just exploding in your hand. Afaik the designer never even released the files for them due to how unsafe they were.

What most 3D printed guns are these days is little more than a really fancy custom grip for an existing model of firearm. Glock uppers are super commonly used and are just fitted on top of the nylon components - these components are also glass-fiber reinforced nylon (or other high strength plastic) on the production handguns, meaning there’s no change in the metal-detectability of the gun. (edit: this is the type of 3D printed gun that Luigi used)

The fear of something like the songbird being used to circumvent a metal detector is a worthy concern, but please keep in mind that you can build an equivalent weapon with ducktape and a metal bodied ballpoint pen, or damn near anything else. If you’re curious, look up ‘zip guns’ for many examples of humanity’s ingenuity with finding ways to kill each other.