It does and doesn't. The outer layer of the durian, yeah that's gone. Dense biomass presents a unique scenario though. Where steel is homogeneous, and conducts heat very well, cells are "hollow" and contain a lot of carbon. Water vaporizes. Proteins vaporize. Carbon burns off. Slightly deeper: water vaporizes. But there's no oxygen here. The burning biomass outside is consuming it and dumping carbon dioxide as it goes. What happens when carbon heats without oxygen? It purifies. Down to pure carbon. 3,630C to melt it away. What's more, it's not solid carbon. All that water and protein is long gone, but now it's empty space. Insulation. It's impressive how much biomass blocks heat.

Time matters. Long enough, the outer layers start to burn away. Oxygen moves deeper, carbon burns, not melts. That layer burns off. Oxygen moves deeper. You didn't need 3000C. But you need time and air flow. If you're trying to see who between a mass of steel or an equal biomass gives up first, the steel will fail every time.