I feel like the author's prose right underneath that heading explains it really well:

  If you silo yourself to only learning within your company, you are missing out on a world of experiences and expertise different than yours from the external community. Technical leaders realize this and place importance on learning from the larger world of computing than just their solo.

New ideas get introduced to orgs in many ways. In my experience, it's primarily through hiring new people, but making it an expectation of distinguished eng is clever, because you can also expect them to practice and apply discernment.