Hmm, for 2E, I can see...
True lycanthropes share a vulnerability to silver weapons, possibly because of the metal's relationship with the moon, or the inherent qualities or powers of the metal itself. Extremely rare variants might have no such vulnerability, but instead may have developed a weakness for another precious metal (gold and copper being the most likely), or perhaps for bronze, obsidian, or even wood.
I had to hunt for the loup-garou specifically; it's from Ravenloft (yuck), but I believe at least one of the designers was familiar with the setting because of some of the other monsters and because the vampires in SoA progress according to the same age classifications (fledgling, mature, old, very old, ancient, eminent, patriarch) that I think were only ever detailed there...
Special Defenses (Mountain): Hit only by +1 or gold, regeneration
The problem I had with cold-forged iron is that there was no basis for it in any resource in any IE game ever released that I'm aware of (unless Kondar is a canon cold iron weapon?). In BG, it's used for Balduran's gold sword (and butter knife!) and is specifically called out that you need gold weapons to damage the toughest werewolfs, and in all the other IEs, it's completely meaningless (in BG2, it's clearly set 99% of the time merely to ensure it always bypasses any "Immunity to weapons: Gold" effect). Regardless of the label, however, you should be free to use it as you wish (I don't think there's anything associated with that flag, other than being able to block it with certain values to the Immunity to weapons effect).