In the AWS Certified Security course, during the KMS Part 4 lecture, at 04:26, the instructor states that importing your own key material can allow you "to be resilient to AWS failure by storing keys outside AWS." How is that possible? Didn’t earlier examples show that you cannot use a new key to access data encrypted with a previous key, even if all of the same key material and wrapping code is used? What kind of failure is this contemplating? Thanks!