Yes. But also any given country completely controls the design of bank notes so they can make sure those marking dots are on the banknotes in the first place, and put on in such quantity and variety that they are hard to remove without making it too obvious.
The thing about 3D models is they are made by anyone, so anyone who makes them would need to put the "this is a gun" marker somewhere on the 3D model. Even if people were willing to do that in principle (unlikely) they would still have to be able to do it in practice. And in a way that would be hard to remove, which is tricky because some parts are presumably functional and can't have weird modifications, and anything else can be modified freely.
With that said there are a LOT of utterly specious arguments in this thread.
The argument "well I can make a working gun using only pipe parts and a toothpick" is a specious one, along with "I'm a skilled machinist and can make guns". They're not wrong, but it takes time, skill and knowledge that most people don't have and won't acquire. If they could they probably wouldn't be robbing liquor stores with handmade gnus. See for example in the UK there are laws preventing under 18s from buying knives.
Any under 18 can cheaply buy tool steel blanks, a low end grinder, etc and make an incredibly good knife. But barriers to entry do actually make a difference because even if someone can theoretically do something it doesn't mean most people can do it in practice.
So something that makes it harder to get guns can absolutely be effective even if it's not 100% watertight.
But this absolutely 100% is not it.