What are you talking about? The asshole works as a die. Extrusion is about deforming the object, it doesn't have to change its general "shape". If there is plastic deformation, which there is as stated(unless you hold it in unhealthily long), then it counts. You extrude a cylinder with a big cross section to one with a smaller cross section.
I never realized that this process is basically a biological cold extrusion.
That's because it isn't. As was just explained, the shape is pretty much set before the "extrusion die" sphincter comes into play.
What are you talking about? The asshole works as a die. Extrusion is about deforming the object, it doesn't have to change its general "shape". If there is plastic deformation, which there is as stated(unless you hold it in unhealthily long), then it counts. You extrude a cylinder with a big cross section to one with a smaller cross section.