Yep, just to add, it's entirely possible to have a melt down without any explosion at all. As you said, It just means the fuel melted through the reactor vessel. It can even happen without the fuel going prompt-critical.

Coolant flow stopped and they pushed the rods in rather than out, compounding the heat buildup. It was a pressure cooker explosion, followed by fissile material melting. It didn’t melt down on its own, it was guided.