That is not true. Once you check in, if you need to bail out, you can do so penalty free. That almost happened to us. We checked in, party of 4, and my husband started feeling bad, and while I was standing in the 20 min line after checking in, I asked the hostess "If we decide not to go in, and we leave now, will we be charged the no show penalty?" She said we would not, we would be fine. So, once you check in, you are "cleared."
They will simply not let you just loiter inside. If you don't order a drink and tell them you don't want anything, they will tell you that you cannot stay.