The default installation of PostgreSQL listens on 127.0.0.1 (the local loopback address) and on Unix sockets. The controlling parameter, listen_addresses, isn’t documented to have a setting that just listens on sockets, and not the loopback address.
As it happens, such a setting exists:
1 listen_addresses=''
Among other things, this appears to prevent local instances of pgAdmin from connecting (although psql works fine), so its utility is not clear, but there it is if you wish it.