So you're assuming Apple is going to go ahead and release with the under-glass sensor even though (your guess) it's working less reliably than their regular FPS... but Samsung is going to wait until it's as good as their capacitive scanner??
You're really putting more trust in that from a company that just released a half baked, useless Bixby button and twice released an exploding phone?
Honestly I would not think Apple would release if they couldn't get it as consistent as their current FPS... and if you haven't used their current sensor, it's pretty good. They have a lot of high expectations on the 10th anniversary phone.
Samsung is going with two companies to get this sorted out cause it sounds like really sounds like it hasn't been fully developed... Apple bought the company that their sensor is based on i believe a couple of years ago and sounds like it's sorted. The only issue I heard was with low yield for mass production.
With the latest Samsung leak... if they just put the button in the middle and under the dual cameras and deliver on the rest... I think people will be ok with it and see if they can't get the sensor right on the S/Note 9.