Marco talked about his decision to require iOS 6 in previous episodes of Build and Analyze.
He wanted to try requiring iOS 6, because it would help him write cleaner code internally, but he actually has a version of the app that will work with iOS 5. Depending on adoption of the iOS 6 version, he may or may not "revert" support back to iOS 5.
https://www.forbes.com/sites/janakirammsv/2017/11/29/google-...
YMMV, but I think the value prop of using a managed GKE cluster vs the raw costs and engineering time to run your own control plane is still strong.