Tippet is also made with an extruder but would be a continuous run of several thousand feet which would make it easier to maintain control. Extruding a tapered Leader would require some sort of on/off, slow/fast process or adjustable die. I'm guessing that "Head Pressure" would vary and thus a loss of material integrity (Strength).
I would also think that in a "Production Run" of Tapered Leaders many would be much stronger but they are all rated based on the weakest.