It may be more common than you think...
An older tank on my grill at home WAS overfilled...or maybe it wasn't. All I know for certain is that I'd had the tank refilled and a couple of days later, when I wanted to use the grill, I discovered that the threaded hose connection had been blown off the tank and the tank was empty. Although all the safety warnings advise keeping the valve on the top of the tank closed except when the grill is in use, I always open it to "test light" the grill after changing the tank and leave it open. Was it overfilled, or did the fitting just fail? If it was overfilled, and if I hadn't left the valve open so the pressure could be relieved by blowing the hose off, what else might have happened? Was mine one in a zillion, or do the older fittings--like a lot of other things--have a finite lifespan, after which the likelihood of failure increases exponentially every year (mine was only two years old, btw)? These are not questions I'd want to learn the answers to on a boat.