For the Google pixel I just want the option to use fingerprint instead of it plus a pin or anytbing. This is just cause I'm using echo lock screen and I still like waking my phone up with my fingerprint.
3rd-party lock screen apps have been known to cause the double login. I know that was the case, I don't know if any figured out how to get around it or not as I just use the stock lock screen on my Nexus 6P.
In fact, looking at the comments on that particular one, other people are complaining about the same shortcoming.