What significant change occurred with Apple Diagnostics in June 2013?

The significant change that occurred with Apple Diagnostics in June 2013 was that it replaced the Apple Hardware Test for new computers. This transition marked a notable update in how Apple provided diagnostic tools for its hardware. Apple Diagnostics introduced a more streamlined and user-friendly interface which allowed users to run tests on their Macs to identify hardware issues more effectively.

This change was part of Apple's efforts to enhance the user experience, providing a more comprehensive and accessible way to diagnose hardware problems without needing the old Apple Hardware Test. The adoption of Apple Diagnostics reflected advancements in the technology and a shift towards a more integrated diagnostic experience for users of newer Mac models.

While other options address different situations or technologies that are not related to the replacement of the Apple Hardware Test, the core focus on Apple Diagnostics transitioning to take its place is why this choice is significant in the context of the Apple's diagnostic tools for their hardware as of mid-2013.