Clutch head. Used to be common before the factory switched over to Torx. In a few years they will find another fastener to use that no one else has to limit the number of amateurs working on their cars.
Before the Torx and clutch head they used a Philips head and before that a Robertson head Square drive. In reality it is all about what can they use on the assembly line to increase production. So they use a driver that will not slip out and can transmit a lot of torque. Allen heads have never been used as it is too hard to get the driver on the screw to meet production demands.
Big Dave (retired Industrial Engineer)