I think that is part of iOS and the real question is which app (likely third party) is causing that to be present enough to show up in the screen time usage.

My guess is this is the service that has the backlink feature in the top left near the time. So when you open an app, you can easily go back to the previous app.

But, it seems like a bug in iOS that this shows up in your screen time.

My guess is it’s the process that controls the tiny button in the status bar that takes you back to the previous app you were in.