It's consistent enough. I can log in using it every time except immediately after startup, and that alone is a big saving of time and effort. Same with my not having to unlock 1Password manually all the time.
You also need to type your password the first time after you restart your iPhone or iPad, with TouchID or FaceID. It has nothing to do with how "secure and reliable" biometrics are, it's just another layer of verification right after startup. If your MacBook had FaceID it would be the same thing.
And no, it doesn't slow the user down more to have to occasionally type a password, versus having to type it every time no matter what.