The Torx bit is designed to not slip out when torque is applied, unlike common flat or Phillips screws. It is a newer design and technically superior to older forms. However, the inverted Torx bit is usually used by manufacturers to limit the consumer's access. If the consumer can't open the product, they can't make the problem worse. The idea is that if someone has an inverted Torx bit, they probably have the mechanical know how to fix the problem.