Most polymers show a phase behavior that is different from water. Cheese is a mixture of biopolymers. A typical polymer, say polystyrene, will exhibit three phases, glassy, viscous or rubbery, and melted. For some, the melt temperature is higher than the decomposition temperature. You can get cheese into its rubbery viscous state, usually, but it's not a true melted state unless you add a lot of stuff.
Of course, in cooking, we don't distinguish between viscous rubbery and melted. The stuff appeared to liquify so we're happy.
The oddity of the glass transition is that it is time dependent. But that's a longer story.