Whats are non-craftable prefixes?

I came across something while viewing the wiki for salvaging. It says Exotic weapons and armor with non-craftable prefixes also have a chance to produce an inscription or insignia for that prefix.

That literally makes ZERO sense considering all crafted gear requires one of those because where else would it get its stats. So how can something that cant be crafted yield a insignia used for crafting when you salvage it????

The stats that don’t have a t6 material to represent it are the non-crafted ones. You get the insignia and inscription from salvaging items with these stats. Usually from drops in Fractals, which often are Soldier stats, or dungeon vendor items, which are Dire, Cavalier, Rabid, Magi.

The idea is: if you can craft an insignia, there's already a source for it in game, so it doesn't need to drop as part of salvage.