It isn't about whining, it is about usability and consistency. The new TouchID sensor wasn't designed for better apple pay, Apple Pay was never an issue with it because the NFC read takes longer than the fingerprint scan. The sensor was put there to unlock your phone faster which people do countless times per day.
The problem with the old sensor is that you get used to moving your finger off faster, so you end up having to scan twice because the last 100 times you used touch ID on your phone it was lightning fast, and now you are unlocking your iPad using the same gesture and it is not the same experience.
If iPad Pro was a $500 device, then sure that is cool, give it to us next year, but it costs $1000 and is not something that people are going to be upgrading every year like an iPhone or even an Air/Mini, especially if they change the form factor and break compatibility with $160 accessories.