The intention of using the Apache 2 license goes beyond this as well. This isn't just about Apple's contributions to the Swift project, but any company that has a significant patent portfolio such as IBM and Google. A contributor whose contributions implies one or more of their patents is effectively contributing the use of those patents to the Swift open source project. This was intentional and by design.
Any company making a contribution to Swift is intentionally licensing implied patents to the project. This is a business decision. Speaking on Apple's behalf, that business decision is clear and deliberate: we want Swift to be successful and to be used widely. The Apache 2 license provides a form of IP licensing as well as IP protection for the project, and thus its users.