I've received plenty of things from stations that show up on the unconfirmed list. I'm not sure exactly what the USCG defines that as, but I'm guessing perhaps some monitoring is broke or intermittent and they cannot guarantee the service is accurate, even though it still transmitting. Or something like that.
Since we don't care about the contents of the message, other than a valid format, that status isn't too exciting. But, when a station has degraded power or off the air, that's very interesting as that may/will cause changes in which stations come in.