But how much more convenient is it really? Filling out the login form with Bitwarden is a single hotkey: Ctrl+Alt+L. That's such a light burden that I'm having a hard time seeing the value proposition for users who are already on a password manager.

I can totally see the value for companies who serve users that don't use password managers—if you can get those people onto passkeys that's a clear security win.

My passwords are bound to a domain and Bitwarden will refuse to autofill if the domain doesn't match. I can copy the password manually if I care to, but that's true in every passkey implementation that I've seen as well: they're never the only login option, you can always log in with a password too.