In a response from Apple PR to journalists about my HOPE/X talk, it looks like Apple might have inadvertently admitted that, in the most widely accepted sense of the word, they do indeed have backdoors in iOS, however claim that the purpose is for “diagnostics” and “enterprise”.
The problem with this is that these services dish out data (and bypass backup encryption) regardless of whether or not “Send Diagnostic Data to Apple” is turned on or off, and whether or not the device is managed by an enterprise policy of any kind. So if these services were intended for such purposes, you’d think they’d only work if the device was managed/supervised or if the user had enabled diagnostic mode. Unfortunately this isn’t the case and there is no way to disable these mechanisms. As a result, every single device has these features enabled and there’s no way to turn them off, nor are users prompted for consent to send this kind of personal data off the device.