I've noticed that when I double tap to pay from the lock screen, once the card image is present I can single tap and bypass the code/touch id. This is a pretty serious security flaw.
iOS 9 Lock code sidestep when using double tap to pay
I tried this with my thumbs that are in my touch ID and it did the same but then tried with fingers that are not in my Touch ID and it didn't work so I think it's only unlocking on the single tap for you because it's aquired your finger print during the three seperate presses.