Apple hired Foxconn to do OEM work. Why is it not afraid that the technology will be leaked to Foxconn and Foxconn will make it itself? Thank you all

Foxconn has a very strong product manufacturing capability. Don't imagine how unattainable Apple is. In the research and development process of Apple products, Foxconn has played a very important role. For example, Apple has an idea, and Foxconn has to study the manufacturing process to verify whether this idea is feasible. Therefore, Foxconn has a lot of technical patents in these areas, such as molds, metal processing, material technology, and so on ~