It's certainly possible to end up above cloudbase without flying in the cloud or breaking rules. Years ago, I flew from southern Arizona over the Chiricuhua Mountains into New Mexico to find myself over the tops of cumulus clouds on the other side of the hill! On another occasion, I flew out of the top of a thermal into wave that took me well over clouds that day.

Having said that, if someone is using instruments to cloud fly to get an advantage, it will be readily noticeable.

Mike