[reanimated]

The theory about the iOS 13.0 is that Apple was forced to updated to this buggy iOS version because of Apple Watch release. Watch was shipped with watchOS 6.0 already installed and it requires iOS 13. iOS 13.1 was still not finished and to prevent situation where new watch customers couln'd use it after the purchase - they needed to update as it is.

[mkasu]

That I was hinting at in the last sentence. Apple Watch 5 and iPhone 11 came out on the same day and needed watchOS 6 and iOS 13 respectively, so basically, those hardware releases forced the buggy *OS to be released across all platforms and devices.