Garlic and Silver — What's the Big Deal? basically has covered what Is there any scientific reason why only a silver bullet can harm a werewolf? asks.
However, given that these are old questions, should we close the second as duplicate?
Is there even any merit to do so?
The thing is: the sites scope changes. All the time. Most of the time only slightly, but after enough time quite a lot of old questions will be close-worthy. Obviously this is especially true for a younger site like WorldBuilding.
If you start closing old questions because they are not in-scope anymore you would (in a perfect world) have to go through every old question to check whether it should be closed. And you had to do this whenever there is a change to the sites scope. The same applies to reopening by the way. This is just not worth the effort.
From time to time old questions get revived. Maybe someone looked through older posts and decided he can answer one of them. Or someone found something that needs a little copy-editing. In those cases you should VTC a question if there is a valid reason. Just because something has been on-topic before doesn't necessarily mean it's still on-topic for example.
All in all I would say there is no real value in reviving one of those questions as a duplicate.
