It's an inevitable idea.
Also: this 3d printer itself needs a big logistics chain. Not only the printer itself which you can probably buy in 10 years from AliExpress COD Shenzen, but the things like the resins, stable power source, etc.
And they haven't made anything that goes boom yet either, cause a 3d printer is not a good chemical laboratory. Even the propellant is lacking. What good is a grenade that doesn't go boom?
Shooting training grenades isn't very scary.
Just like producing a normal rifle or other firearm once upon a time was high-tech precision manufacturing, making black powder needed lots of bird shit and caused regular explosions in the factory (more high tech), is now something hobbyists can do. So improving technology will making other stuff reachable by amateurs, in this case, grenades.