I think it is a Mapping issue, since the correct answer is probably to pull down on the ring near the end of the faucet.
The faucet end (opening where water comes out) is an object-part that usually lacks interactivity. It does have an interactive affordance, which is the protrusion of the ring that allows downward force. The absence of texture or other typical device inhibits recognition of the function.
Like most non-intuitive UIs, once the user is educated as to the operation, this mechanism is probably preferable over the life of the product (user exposure).