There’s more than one reading of relevance here. The players know where the Werewolves are going but they don’t know why that information would be more motivational to the far than what they have already said.
And they have no reason to trust that it will solve their problem, the fae may simply use the information and fortify or remove themselves from the danger*. Because the players have a problem with where the werewolves are not where they are going. A response to where they are going doesn’t help remove them from where they are.
So without the knowledge that this is the secret password to win the conversation they [i]don’t [/]know it’s relevant and there are predictable downsides to giving it.
*A not unreasonable response, for most entities in direct combat with a werewolf your options boil down to updating your will and telling him your favourite colour so he can have the janitor scrape your remains into that colour bucket.