I quite agree, there should be an option to disable this temporary display. What they are doing is trying to make sure you can use the fingerprint reader as a one press thing, rather than press power button then put finger on scanner.Yes it matters when you turned off the options and it still turns the screen on. "When the screen is off" "don't turn screen on" is check and it still turns on. There was already an option to lift phone to wake if you wanted the screen to turn on. I never said anything about power usage.
I'm sure the option will arrive to turn it off completely. You know Google everything is BETA!