I think you’re right, with this caveat: the players can’t just say, in the middle of the GM’s turn, “Oh, I’m making a Weasel-wise test.” That’s Player’s Turn stuff.
However, I’d think that if the players are chattering about different ways to overcome an obstacle, and they can convincingly throw in their Weasel-wise, i.e. “OK, we’re going to sneak into the Weasel camp with Scout, but first I’m going to test Weasel-wise to see if Weasels are generally drunkards.” That seems really allowable to me, but what say you, Luke or more experienced players?