Non connected transport do not validate the peer (no persistence of peer, stateless so we do not have challenge anymore). Plan would be to have a new query type for ping (usefull also for synch where we always stuck client process waiting synchrously for a pong see [https://github.com//issues/41].
Other plan should be to symply drop non connected transport (make things a bit more complicated and currently not used). See also ref to APONG