I think you misunderstood what I wrote ("making the actual origin of a request unknowable"): of course there is a node that knows your IP address, but no node k

I think you misunderstood what I wrote ("making the actual origin of a request unknowable"): of course there is a node that knows your IP address, but no node knows both the actual origin and destination (not even the user who generated the request in the case of hidden services) in any communication inside the network. The objectively reasonable expectation of privacy is in who, from all the IP addresses that are part of the network, is initiating a communication. Who is entering into a polling place is also "public", yet nobody knows who made certain vote.