Are Twiglets an “extruded snack”?
The additional technical details on extruded snacks are that they are not just extruded but do so under high pressure and temperature, so that as they come out of the extrusion nozzle they puff up and solidify. The rapid transition to lower pressure causes water in the dough to vaporize suddenly, creating air pockets (puff) and removing moisture. Since baking is primarily a process of drying this completes the cooking.

I haven't had a twiglet, but based on the little bit of info available they would appear to be made in the same manner as the bumpy sort of Cheetos, which would indeed make them an extruded snack.

It is conceivable that they are extruded at room temperature and pressure, and then deep-fried, which is the case with some Japanese snacks that otherwise resemble extruded snacks.