Why does my phone sometimes unlock with TouchID, but not go to home screen/app?

I have an iPhone 7 running iOS 11.0.1. I just started using TouchID to unlock the phone, and I've occasionally encountered an unexpected behavior.

I thought that when pressing the home button it would unlock and go to the home screen, or last app. I have on multiple occasions pressed the home button to find myself at the lock screen, with the "Press home to open" message at the bottom, and the lock missing at the top. I can't seem to replicate this with any consistency.

The end result is exactly as if I pressed the hold button to wake the phone, and then touched the home button to unlock.

Is there some specific way that I'm pressing the home button to cause this?

I would prefer this behavior to opening to my last app because my natural grip on the phone makes it easier to press the home button than the hold button, and I like to check notifications on the lock screen.

Are you using raise to wake? There is a timing that is difficult to duplicate, but can be repeated, where you can press the home button and raise to wake at the same time. The Touch ID unlocks the phone, but the wake seems to register from the raise instead of the home button press and so you stay on the lock screen instead of opening to the last app/home screen.

If you want the behavior of the phone being unlocked, but staying on the lock screen so you can look at your notifications, then just raise to wake, rest your finger on the home button, but don’t press until you’re ready to leave the lock screen.