For a warden that would be true through ... it's like an NBA star telling you that dunking is just jumping up to the basketball basket. In hindsight surely you can easily attribute that to his fabricated identity, but within the context of wardens and their secrecy it is just "yeah we just need to stab it, that is all you need to know". That is literally what we do in DAO, some of us just bed a witch first
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I'm pretty sure they're just supposed to cite "warden secrets", not lie and say there's nothing to it. If there wasn't anything to it, then you wouldn't need wardens. There's no reason for the wardens to be freaking out about the calling unless there's something special about wardens that allows them, and only them, to stop an archdemon.