How does the new back to previous app work

I’ve noticed that After the last update when you click the back to previous app icon it just brings you to a blurry version of your Home Screen instead. I really like this fiction because when you had to click away from an app to answer a tex/email/whatever you could just click back to previous app, and it just happened. It was quick and convenient. I don’t get what is up with the newest version. Am I using it wrong? Please help!