This announcement is partially about the platform-integrated authenticators being made into 'virtual' authenticators backed by a platform vendor-specific cloud

This announcement is partially about the platform-integrated authenticators being made into 'virtual' authenticators backed by a platform vendor-specific cloud ecosystem. So for example, a credential registered on an iPhone may be synchronized over iCloud Keychain to work to log in my Mac via TouchID. This is something which has always been as part of the model - an authenticator is just an abstract thing that represents an authentication factor, generates keys for a particular use, and doesn't share private keys outside its boundaries. This announcement possibly marks a transition where sites supporting Web Authentication (with a bring-your-own-authenticator model) will go from seeing 90%+ hardware-bound authenticators to seeing 90%+ platform-integrated, synchronizing authenticators. Bundled into that prediction is a hope that this (and other proposed changes) will lead to a 10x increase in adoption.