This is nothing new, although there's perhaps no common standard implemented by all the players. However, while the process may be "simpler, securer ways to grant login access" from the users' perspectives, often these sorts of protocols become many times more complex to get right on the server side of things.
Another worry is that this sort of approach will effectively hide the authentication mechanism from the user. So while I may make the choice to use notional biometric login to a Facebook app on my phone, knowing all the risks and compromises that come with having a Facebook account, I may not wish to use a Facebook login for other authenticated services unrelated to Facebook (when I'm confronted with the option to log in with Facebook, I always choose the other option, whatever it is, even if it's "give up on using this system/service").
Authentication and Federated login shouldn't become the same thing, and FIDO doesn't move us closer to that. There's not a scenario where this becomes "silently login to Facebook and silently provide consent by clicking login" - users will still have to consciously click on "login with Facebook" at which point they can use FIDO to login to a Facebook property.
Another worry is that this sort of approach will effectively hide the authentication mechanism from the user. So while I may make the choice to use notional biometric login to a Facebook app on my phone, knowing all the risks and compromises that come with having a Facebook account, I may not wish to use a Facebook login for other authenticated services unrelated to Facebook (when I'm confronted with the option to log in with Facebook, I always choose the other option, whatever it is, even if it's "give up on using this system/service").