John Gruber, Should iOS 10.3’s App Store Rating Prompts Be Notifications Instead of Alerts?, on 2-02-2017:
There’s no question that the current design in the 10.3 betas (the modal alert) is more intrusive. But developers get to decide when it appears.
No matter how well developers think through the issue, they will never be able to even approach 100% accuracy on the best time to ask for a review. Even in apps I love, it’s almost never a good time at the moment for me to fill out a review as I’m doing something, but I do want to be able to come back later, like when I’m going through notifications and have some downtime, and be able to review it. To me the issue is simple: it is least intrusive and most efficacious for the user to have review prompts be notifications and not modal dialog boxes.