When I read the keynote highlights I assumed Apple were extending the existing (iCloud) Keychain/Safari integration to include username generation, and obfuscated email generation resolving to your iCloud account. Since they implemented 2FA codes auto filling in the QuickType bar in iOS 12, they could've extended this UX further, or used 'Siri suggestions' to complete email verification.
I assume they didn't take this approach as it's harder to present a consistent call to action to initiate sign up, but it seems like a missed opportunity to me.
Does anyone know of a password manager that allows you to generate unique email addresses as a part of the core UX?