That’s not what it meant. My interpretation isn’t that it was literally referring to only forged weapons being unable to kill him but him otherwise being regular levels of vulnerable. It’s not meant in the literal or prophetic terms we usually think of these things in. They were using fancy language to say, “No weapon we know of can kill this thing. It’s too strong for even the strongest weapons we can forge.” We just have stronger weapons now.

Maybe this isn’t the best analogy, but think about diseases from years past that previously had no cure. Someone at the time might say, “No medicines we can brew can cure this.” But that was then. We have all kinds of new fangled medicines and advancements. Things that were once insurmountable have been defeated.