However, an amount of consistency is still required. If bronze has very different material properties in one context than in another, things start to get weird, and players may feel that becomes disconnected from a feeling of reality. It doesn't seem reasonable that Gloranthan bronze would be better than medieval weapons-grade steel, for instance, and if it is, that opens up a huge can of worms.
Further, once bronze starts to not behave like bronze, or perhaps a slightly better Gloranthan bronze, what can we even tell about it any longer? Meanwhile, if bronze is at least mostly bronze, we can apply our real-world ideas to it - it has to be cast, it has to be handled the way real-world bronze weapons are, we can assume it gets hammer-tempered, and so on. If it gets too disconnected, we can only know what the game tells us. At that point, why even call it bronze in the first place, if all it does is mislead?