Re: Fingerprint sensor placement concerns? Wait till you read this.
Coming from an iPhone 6s Plus, it will be a little annoying at first. I think the biggest argument for putting it on the back of the phone is now you have to pick it up to unlock it using fingerprint authentication. Since it is wireless charging that could be inconvenient if you have to remove it from the charger to unlock it.
As far as comparing it to the pedals of a car. That is a bad analogy. Pedal placement in cars is an international standard. The gas, break, and clutch are in the same spots on a right driving car as they are on a left driving car. The difference is the placement of the gear shift, turn signals and the windshield wipers.
If there was a defacto "standard" of where the fingerprint scanner is, then I would think there is a problem, but since there isn't, the argument about its placement is moot.
Samsung is not the first to place it on the back, nor will it be the last. It is the same argument when LG put the volume and home buttons on the back of the G3. There were a lot of complaints, but ultimately they kept that format.
I think if Samsung put it underneath the camera like on the Pixel or the G7, then there would be less complaining.