What? Maybe in Germany, but that is not the case in the US where the biome has only been exposed to humans for 1/10th the amount of time as in Europe. “Native” is pretty strictly defined here ecologically, legally, and culturally.

Polyurethane is made by (among other steps) mixing paint thinner and phosgene gas. It’s a nasty dangerous process.

The only time plants are involved is when they mix in some fiber pulp at the end.

Plant based plastics exist, but they are not polyurethane.