It depends on how you look at things, in this case you and the search service provider are both signal clients and the proxy is the signal server that relays th

It depends on how you look at things, in this case you and the search service provider are both signal clients and the proxy is the signal server that relays the messages between the clients and provides privacy on the network level (hides the IP). Since the proxy cannot decrypt the query or the response it can’t see anything. Wether the actual privacy as in is it possible to correlate queries to attribute a search to a given user is always preserved it’s hard to tell without looking at the implementation in depth but it provides some level of additional privacy at least to the level of a VPN.