挙動の変更について、Xcode 10.2で公開されたドキュメントに何も書かれてない

https://developer.apple.com/documentation/swift/string/index/2922827-init?changes=latest_minor https://developer.apple.com/documentation/swift/string/index/2922802-encodedoffset?changes=latest_minor https://developer.apple.com/documentation/xcode_release_notes/xcode_10_2_beta_release_notes/swift_5_release_notes_for_xcode_10_2_beta

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