Wolf Stance monk feat (CRB p159) :
You enter the stance of a wolf, low to the ground with your hands held like fanged teeth. You can make wolf jaw unarmed attacks. These deal 1d8 piercing damage; are in the brawling group; and have the agile, backstabber, finesse, nonlethal, and unarmed traits.
If you’re flanking a target while in Wolf Stance, your wolf jaw unarmed attacks also gain the trip trait.
Even if you have the Monastic Weaponry feat, Wolf Stance does not give you any benefits if you do not have a hand free. But if you have a hand free, you can use Trip anyway.
So what exactly is the point of the highlighted sentence of the feat?