I've heard that argument, but no one ever seems to mention that FPS is not required to unlock the phone. Sure its quicker, but not required. Personally, i'm not sure how I feel about the location yet, but the FPS on the S7E was crap for me, so any improvement at this point would be welcome.
Of course.
But if locked on a desk with screen side up, which method is faster?
Pressing the front FPS.
Waking the screen, entering your PIN or pattern
Picking up the phone, press the rear FPS
For a lot of people, a front FPS is more convenient.